Water temperature for hydroponics


Hydroponic Reservoir Temperatures

With summer coming up fast, an important topic that often gets overlooked that any grower who keeps a reservoir must deal with; reservoir temperature.

For those who use true hydroponic systems, such as Deep Water Culture (DWC), or keep a large reservoir of nutrient solution, it’s important to maintain your solution within a specific range to avoid major plant health issues arising.

The optimal temperature to keep your nutrient solution at is between 17℃ (63℉) to 22℃ (72℉).

If a reservoir’s nutrient solution temperature drops below 15℃, the plants growth will retard and eventually halt all together until temperatures rise. The upside of having a cooler reservoir temperature is the potential for increased dissolved oxygen, but to utilize this you need to stay above the 15℃.

If a reservoir’s nutrient solution temperature rises above 22℃, the plants access to dissolved oxygen will decrease, leading to a significant rise in anaerobic pathogens, such as Pythium (Root Rot), which is all too common in warm reservoirs, eventually killing your plants if unable to control. Most people can get away with few hot days here and there, even if your reservoir hits up to 30℃, but anytime you hit high temperatures, you always run the risk of pathogens overtaking your roots.

Another common side effect of having a hot reservoir leads onto nutrient concentration; if your reservoir becomes too hot, its nearly always a product of a hot environment. If your environment is hot, your plants will need to cool themselves via perspiring, which will result in your plants drinking significantly more water than usual, and in most cases, drinking only water, and not nutrients.

For those running in Deep Water Culture systems, this will increase the nutrient concentration of your reservoirs as the water is removed but the nutrients remain, increasing your EC/PPM. If your solution loses water at a significantly higher rate than losing nutrients, your solution runs the risk of becoming too concentrated and burning your plants, eventually leading to a complete nutrient lock out and serious plant health problems.

Avoid the gamble, chill your reservoirs!

Cooling your reservoirs

With summer just around the corner, we’re going to take a look at options to cool your reservoirs down.

Water Chiller

By far the most effective way to cool a reservoir: A Water Chiller.

While this method is the most effective and reliable, its also the most expensive, as water chillers for either Hydroponic or Aquarium use can set you back a few hundred dollars at least. Depending on your growing location and climate, this may be your only option if you wish to grow through the summer months with any real significant reservoirs.

Insulating your reservoir

This method is highly recommended for anyone needing to lower reservoir temps, as this technique can and should be implemented along side with any other method for keeping your temperatures down. Simple and cheap adjustments, such as painting or wrapping your reservoir in Mylar or white reflective surface covers can drop your temperatures down for very little cost.

Increase your reservoir size

A smaller reservoir will heat up significantly faster than a larger reservoir, as more water will take longer to heat, and vice versa. With good insulation and a large reservoir, it should buy you some more time to get through a hot day without as much of an increase in temperature, although this isn’t always an option for everyone and posses some other potential issues for having a huge reservoir.

Remote reservoir location

Some growers will store there reservoirs away from there grow space, in a room or area with much greater environmental control, pumping to and from this room, to their grow space. Some growers will even go to lengths such as burying this reservoirs unground as a natural insulator, although these are not always an option for everyone.

Hydroponics is an agriculture method that involves growing plants in something other than soil.

There are a few different approaches to hydroponics. Sometimes the roots are supported in perlite or gravel. Often, however, no growing medium is used; plants are suspended with their roots immersed in the nutrient solution.

The key difference between traditional growing methods and hydroponics is how nutrients are applied to roots. While in traditional agriculture roots receive nutrients via soil, In hydroponics nutrients are supplied to plant roots via mineral nutrient solutions in a water solvent.


What’s in a hydroponic nutrient solution?

Essential nutrients included in the nutrient solution are: Nitrogen, Potassium, Phosphorus, Calcium, Magnesium, and Sulfur

Additional nutrients that may be included are: Iron, Manganese, Boron, Zinc, and Copper

Water: Temperature is Critical!

As mentioned above, hydroponics typically involves a plant’s roots being suspended in a water solvent. Because the root of a plant is the start of its vascular system (where nutrients are absorbed), it’s crucial that this area is well cared for. Extreme temperatures around the root will diminish a plant’s capacity to absorb nutrients and water.

Best Temperature for Hydroponics

To keep plants thriving, the nutrient solution and water solvent must be kept at proper temperatures. Experts agree that the best water temperature for hydroponics is between 65°F and 80°F. This temperature range provides an ideal setting for healthy roots and optimal nutrient absorption. To get a bit more technical, when temperatures are between 65°F and 80°F, high levels of dissolved oxygen are available at the root zone. Additionally, these ideal temperatures encourage plant disease suppression.

When things get too hot: Cooling Options for Hydroponics

Maintaining ideal water temperatures often means incorporating some sort of process cooling solution during hot summer months. Here are a few ideas to help keep things from overheating:

  1. Ice Packs

A simple, inexpensive solution is to keep 10-15 ice packs on hand and add one to your reservoir every 15 minutes until the desired temperature is reached. This method may become time-consuming when temperatures are especially high and are likely not a viable option for larger gardens.

  1. Cool Water

Another easy solution is to add cool water to your reservoir. Remember that anytime you add water the nutrients will become diluted; check and adjust accordingly.

  1. Paint it White!

Painting your reservoir container white will reflect sunlight and heat and help keep your water and nutrient solution cool. This may not keep things quite cool enough when temperatures are especially high, but certainly helps prevent unnecessary heat.

  1. Hydroponics Chillers

Chillers are an investment, but for larger operations or serious gardeners, they are the most reliable, effective, and easy to use option. Hydroponic water chillers remove excess heat from your hydroponics system and keep things at a consistent temperature without very much work on your part.

North Slope Chillers are an excellent option for hydroponics cooling. They are easy to install and will not disrupt your current layout. Additionally, North Slope Chillers offers custom solution– no matter what your garden looks like, we can help you keep it cool! Shoot us an email at RTHSLOPECHILLERS.COM if you’d like more info. We’d love to help you out!

Hydroponic Water Temperature: What Is The Ideal Water Temp For Hydroponics

Hydroponics is the practice of growing plants in a medium other than soil. The only difference between soil culture and hydroponics is the manner in which nutrients are supplied to the plant roots. Water is an essential element of hydroponics and the water used must stay within the appropriate temperature range. Read on for information about water temperature and its effects on hydroponics.

Ideal Water Temp for Hydroponics

Water is one of the mediums used in hydroponics but it is not the only medium. Some systems of soilless culture, called aggregate culture, rely on gravel or sand as the primary medium. Other systems of soilless culture, termed aeroponics, suspend the plant roots in air. These systems are the most high-tech hydroponics systems.

In all of these systems, however, a nutrient solution is used to feed the plants and water is an essential part of it. In aggregate culture, the sand or gravel is saturated with the water-based nutrient solution. In aeroponics, the nutrient solution is sprayed on the roots every few minutes.

Essential nutrients that are mixed into the nutrient solution include:

  • Nitrogen
  • Potassium
  • Phosphorus
  • Calcium
  • Magnesium
  • Sulfur

The solution may also include:

  • Iron
  • Manganese
  • Boron
  • Zinc
  • Copper

In all systems, hydroponic water temperature is critical. The ideal water temperature for hydroponics is between 65 and 80 degrees Fahrenheit (18 to 26 C.).

Hydroponic Water Temperature

Researchers have found the nutrient solution to be most effective if it is kept between 65 and 80 degrees Fahrenheit. Experts agree that the ideal water temperature for hydroponics is the same as the nutrient solution temperature. If the water added to the nutrient solution is the same temperature as the nutrient solution itself, the plant roots will not suffer any sudden temperature shifts.

Hydroponic water temperature and nutrient solution temperature can be regulated by aquarium heaters in winter. It may be necessary to find an aquarium chiller if summer temperatures soar.

Several Important Aspects Using A Hydroponic Reservoir

The nutrient solution within a hydroponic reservoir should always be full with a larger container (for extra space) that has a lid to lessen evaporation. Depending on your gardens size and environment, on average, it will use 5 – 25 percent of nutrient solution a day.

Large volumes of nutrient solution in your hydroponic reservoir will help to minimize any nutrient imbalances and give more buffering if you add too much nutrient to the reservoir.

Always check the level of your hydroponic reservoir every day and top off with either water or nutrients if necessary. By using up as much nutrient solution before changing it out will help you save money since you will not be draining it all out and down the drain.

Pumps on hydroponic reservoir systems should be set up to lift the solution out of the reservoir. By setting the reservoir high enough you can easily siphon or gravity flow it into a drain or to an outdoor garden.

Hydroponic Reservoir Temperature

The temperature of nutrient solution should always stay between 60 – 75° F (15 – 24° C) for plants to readily take the nutrients up and not shock the plants. Water holds more oxygen when the temperature is at 60° F (15° C) than it will at 75° F (24° C).

Heat nutrient solution is better than heating the air in a room since the reservoir will radiate the heat out and provide the room with warm air (though it may not be fast or enough to heat the room).

A temperature above 85° F (29° C) in the nutrient solution holds little oxygen and can easily damage plant roots.

The nutrient solution that has a temperature around 60° F (15° C) will help you to control transpiration and humidity within the room while also promoting more nutrient uptake for plants. An air pump submerged in the hydroponic reservoir will aerate the solution and help the temperature to level out.

Irrigation With A Hydroponic Reservoir

Irrigation is something that will depend upon many things and must be adjusted to your own garden since one setup will not always work for every garden. Irrigation cycles depend on plants size, climate conditions, and type of growing medium that is being used.

Mediums that are easily drained will need watering more often than others like vermiculite. Top-feed systems generally cycle for about five (5) minutes or longer and irrigated at least three (3) times a day.

For fast-draining mediums overhead irrigation is continually cycled twenty-four (24) hours a day. During and after irrigation the nutrient concentration between the bed and reservoir should be at the same concentration.

If enough time passes between cycles, they may be different and by experimentation, you will be able to find out more so you will be able to make adjustments.

Nutrient Disorders w/ Hydroponic Reservoirs

When the hydroponic garden is regularly maintained and the grower knows the crop well, most nutrient problems can be averted.

If nutrient deficiencies or excesses occur in your system to one or more plants, check irrigation fittings and tubing to make sure that they are connected properly with no kinks disrupting the nutrient flow.

This will ensure nutrient-challenged plants are being properly fed. Be sure drainage channels are not plugged or sitting in stagnant solution since this will rot roots rapidly.

When checking the root system be sure to check the pH to make sure it is within the 5.5 – 6.5 range in the hydroponic reservoir. If there is a nutrient disorder and changing the solution does not solve the problem then try changing to a new brand of fertilizer.

The treatment for nutrient deficiencies or excesses must be taken care of immediately since hydroponic systems not to have a buffer and the deficiencies or excess can affect your plants very quickly. Nutrient deficiencies or excesses diagnosis is rather difficult when two (2+) or more elements are deficient or excessive at the same time.

Taking care of over-fertilization is easy by flushing the system twice (2) with fresh dilute (5 – 10 percent) nutrient solution and this should take care of more problems. Nutrient disorders affect a plant strain at the same time as other plants of the same strain so the nutrient solution is due to being identical how it affects the plants.

Different plant varieties will often react differently to the same nutrient solution. When you are growing one plant strain in a hydroponic reservoir system is often easier to fix than having multiple plant strains within a system.

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One of the more annoying problems we deal with as hydroponic growers is keeping an oxygenated root zone at the perfect water temperature. It’s crucial to squeeze as much yield out of our plants as possible and minimize the potential of disease and infection. However, keeping your hydroponic reservoir cool can be a challenge.

Why Do Roots Need Cool Temperatures?

Most indoor hydroponic growers that use a deep water culture system will run into the reservoir temperature issue at some point in a grow. DWC systems tend to heat up quick when under high wattage HID lighting.

This bumps up the temperature of the nutrient reservoir, which increases the temperature around the root zone. Because of this, the amount of dissolved oxygen in the root zone is lowered. When you combine these factors with plants growing faster in a hydroponic environment, you’ve created the perfect storm for oxygen deprivation. And when that happens…you open yourself and your grow up to pathogens like pythium.

For best results, you want your air temperature to be higher than your water temperature. Typical ranges are 75-80F (23.9-26.7C) for air temperature, and 68F (20C) or lower for water temperature.

Even though roots grow better at the slightly higher temperatures of 70-75F (21.1-23.9C), you would be inviting in pathogens and root diseases that thrive at these temperatures as well. Keeping yourself and your roots safe means operating under 68F.

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So, How Do I Cool My Hydroponic Reservoir?

There are a variety of good ways to cool down your reservoir, ranging both in price and how annoying they are to deal with on a daily basis.

Regardless of the method you choose, you have to ramp up your cooling efforts in the warm summer months – especially if you use a deep water culture or small-reservoir system (the small reservoir size heats up faster).

Buy a Chiller

The most effective (and most expensive) method is to buy a water chiller. These are electric units similar to air conditioning units that are made for operating underwater. They’re basically composed of fans, compressor coils, and a refrigeration line.

All you do is plug and play with these bad boys. To cool water even quicker, make sure you’re circulating your nutrient mixture.

Most commercial growers will use a 1.5-2 horsepower chiller to handle most of the cooling responsibilities and then manage the rest on a case by case basis.

Recommended Water Chillers

  • Active Aqua 1/10 HP
  • Active Aqua 1/4 HP
  • CoolWorks Ice Probe

Paint Your Reservoir

Darker colors absorb more heat. If your reservoir is made of a dark plastic, consider painting it a lighter color – preferably white – to reflect some heat. Using something as simple as white spraypaint can do the job and knock a couple degrees off of your reservoir temperatures.

Keep It In The Shade

This is a really obvious tip, but I feel like I had to mention it. If you can minimize the amount of light hitting the reservoir itself, you’ll be minimizing the amount of heat that is transferred to your nutrient solution. Keep it in a shady area of block the surface with cardboard or aluminum foil.

Increase The Size Of Your Reservoir

Many hobby hydroponic growers use smaller reservoirs which are exceptionally prone to temperature fluctuation. By building or buying a larger nutrient reservoir like this 75-gallon monster, you can add some stability to your temperature without building or buying any other cooling materials.

As an added bonus, your pH and ppm will remain more stable as well due to the larger volume of water.

Top Off Your Solution

An elegant solution is to simply add cooler nutrient solution to balance out the temperature in the reservoir. This isn’t a solution you can use all of the time, because chances are high that if you have a temperature issue, it’s a persistent one. Just use this as a spot-fix if you have a one-time temperature fluctuation.

Note: If you add cooler nutrient solution quickly, the drastic temperature change could shock your roots.

Bury Your Reservoir in The Ground

If you’re growing outside, you can dig out the ground and bury your reservoir. The cool, dark environment below the surface of the soil will keep the reservoir exceptionally cool. You’ll almost never go into danger zone temperatures in the root zone if you use this method – but it does require a lot of effort.

Make Your Own Cooling Coil

If you don’t want to go for one of the more expensive water chillers you can try to make your own cooling coil. I’m not going to go into the details of how to do that in this post, but there’s a great article here about it: http://www.instructables.com/id/How-to-make-a-wort-chiller-for-homebrewing/

Make a Swamp Cooler

A swamp cooler is a pretty ingenious cooling method – I didn’t know about it until I ddi some research. If you take a simple clip-on fan and blow it across the top of the reservoir, you will see incredible temperature drops. You can expect a 5-10F decrease in temperature…but at a cost.

Usually you’ll need to top up your reservoir more often, because swamp coolers are utilizing evaporative cooling (meaning you’re losing water to the air). If you think about this deeper, this also means that your ppm will increase due to evaporation…so be careful if you use this technique.

Do you have any other methods you’ve used to cool your hydroponic nutrient reservoir? Let me know below!

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Kevin Espiritu
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what tempture dose the reservoir have to be?

Get this it is quite simple. I agree that if using a soil system where water is merely poured over a poorly breathing and poorly draining media then increasing the DO in the reservoir is a good idea. I already expressed that. However, this is a aero and hydro thread section meaning I do not give arats ass about soils grwowing problems when addressing issues in this forum section. This is not a soil growing section of the forums. As far as bubble phonics the aeration creates bubbles. Those bubbles have a huge surface area instead of little surface area such as a reservoir full of waer. Increasing the DO in the reservoir serves very little benefit in a bubblephonic system as the massive surface area of the bubbles proprotionally to a simple reservoirs surface area assures there are huge amounts of oxygen present regardless of waht small difference trying to boost the reservoir DO level can possibly make.
Spraying reservoir nutrients in the same way assures a huge number of small droplets of water. Proportionally you are again receiving a huge surface in contact with O2 so that contributes to huge amounts of oxygen being within thw water. Consider a reservoir with 4 square feet of surface area. How much water is incontact with the air inorder to take up oxygen. Now take the same amount of water as n that reservoir and increase the surface area a few thousand fold (actually many thosand fold) by turning the water from its surface layer into many, many, thousands of water droplets all with therir surfaces exposed to the iair so as to take up oxyge.
Or take the water and spread it as a thin layer orver a media with a huge surface area as we are talking the combines surface area of every media particle. That is exposing thw water to a huge amount of air and therefore assuring a high DO. A hydro system is like a trickle filter in that the nutrient water flowing over a very open media insure a huge amount of oxyge. Period.
Either of these last two methods (aerp o or hydro) assure much higher DO than a circulating pump or asome airstones in a reservoir can provide. None of these systems depend on an initial amount of high DO water. These systems (aero and Hydro) create high DO water as they work. Period. They do not need reservoir water tha is high in DO. Period.
High DO water is the chief reason, if any of you ever visited a waste water treatment plant would see, why aeration is applied to waste water in treatment plants. Increasing the amount of dissolved oxygen in water containing high amounts of nutrients cause rapid multiplication of bacteria (biomass) which then convert the nutrients. While this is beneficial when using soil media and organic nutrients it is not necessary with chemical fertilizers in aero or hydro grows as all the fertilizers are already presented in a form where they are easily taken up by the plants roots.
If nothing else consider the best performing aero systems use water contained in enclosed nutrient tanks. No efforts are made to increase DO levels as the systems method of creating a mist creates small droplets of water with a huge surface area in comparison to a reservoir full of water. The system creates a spray with very, very, high DO water even when that water comes from an enclosed reservoir with very low DO water.
The reason a low pressure aero system or a open well draining hydro systenm works so well is because the nutrient delivery systems create high DO nutrients water for the roots use to the roots regardless of the low DO water in the reservoir.
Dragging soil system principles and buubleponics or systems where the roots are immersed in water has nothing to do with the issue that high DO water in a chemical nutrient supplied aero or hydro reservoir actually creates problems rather than benefiting the plants. Once again the last post brings up unrelated explanations trying to justify high DO reservoir water. There are no plants living with their roots in the reservoir with an aero or hydrosystem, so that total explanation about colder water and natures streams with aquatic plants or what ever is moot.
While evaporation can increase with higher temps there is nor reason for there not to be a lid on the reservoir preventing the potential for high evapration from the reservoir. Look at a high pressure aero system. The nutrients are in a totally enclosed accumalator (pressure tank). Yet those perform much better than a low prseeure system or a hydro system.
You guys as well as the articles are just carrying over to many old ideas that were applicable to soil system with hand watering, emitters and such that did not in and of them selves assure high amounts of oxygen as is already assured with aero or soil less hydro.
Warmer nutrients can when there is a high DO greatly speed the multiplication of bacteria, true. High temps and low DO can give protozoa and edge over bacteria, true. Both the bactaeria and protozoa need time to multiply to obtain any numbers to where they cause much benefit or harm. With the Protozoa were talking about 5 to 7 days, with the bacteria were talking 10 to 14 days.
i.e with hydro or aero don’t worry about boosting reservoir DO as it is not needed. If your worried about temps remove the reservoir from the hot grow area. Insulate your nutrient delivery lines, at least make sure they are at least painted white. Or simply use chlorine or hydrogen peroxide to maintain low levels of protozoa or bacteria even with warmer water. Warmer reservoir water up to the room air temp is no big thing to the plants or their roots.
Roots lying in or supended in warm low DO water is detrimental as it causes root death, which leads to all kids of organic nutrients for bacteria and protozoa to feed on and this then leads to Pyth, but I don’t think anyone is telling anyone to create such conditions as that. Aero tubes should be well drained and hydro media should be well drained. Duh. If you have high temps and low DO you will have have more protozoa than bacteria so less Chlorine or H2O2 is need than if you have higher temps and higher DO. Protozoa are more easily killed off by chlorine or H2O2 than bacteria.
I have many books on aquatic chemistry, biological processes, water treatment, waste water treatment and such. I know how bacteria and nutrients respond to differibng temperatures and different DO levels.
One of my degrees is Environmental Engineering. I assure you I know a great deal about water DO, biological processes in water and soil. Like I said what applies to growing in water, or in soils really has very,very little to do with aeroponics or hydroponics. Hydro and aero are good systems because they avoid the DO issues that are common problems with water grows and soil grows where low DO are problems.
I do not do soil grows or bubblephonics. Soil grows are slow old hat methods. IMHO Bubble phonics do not lend itself well to large systems and are a poorer performing systems then aero sytems which commonly use low, medium or high pressure misters or even hydro systems.
I read the links. A lot of their content is old school stuff that only applies to soil grows. A lot is simply wrong.
Water no warmer than the ambient temperature is not harmful to roots. Typical summer rain falls produce warm water not cold water. The writer puts much emphasis on the hot temps caused by green house grows or grows in hot grow rooms.
The somewhat arbitrary temperatures used or an ideal reservoir water temperature is based upon the fact that CO2 is only at levels adequate to grows at temps up to the mid seventies. However most growers who have moved up to hot aero and hydro systems use supplen mental CO2 so that arbitrary temp is out dated.
So stating water should be no warmer than that has just stuck with those outdated low CO2 limited systems and wrongly keeps being stated as what is need even for systems not being limited by CO2 levels.
Dissolved oxygen levels as said in the article and again by me is not an issue with hydro or aero where the contribution of reservoir DO is of little consequence, therefore the need to keep temps low in the 70’s to allow for higher DIO is not needed.
But once again old school thinking is hard to do away with. Very often (nearly always) that water is warmer than the roots temperature a few inches below the ground an a lot warmer than the roots temperture deeper than that. If the hih nutrient temperature in an of itself was detrimental there would be no plants on this planet. The more informative of the write ups is simply stating that colder water slows the multiplication of bacteria anf protozoa. That is true. But it is a simple fact that a very small amount of chlorine or H2O2 does this much more effectively much more cheaply than can any method used to lower the reservoir temperatures. The articles does not address the fact that high DO increases bacteria multiplication even with cooler temps.
Nor does it address the fact that aero or hydro sysy tems just don’t need high Do reservoir water. I acn’t underastand why a group of people who wy ill spend huge amounts om nutrients and most worthless nutrieny supplements would worry about the use of a very small amount of chlorine or H2O2 to solve a bacteria or protozoa problem that may develop in warm resrvoir water in reservoirs that are not changed out often enough to minimize the problem. All facts be known cold nutrient water is much worse than warm.
So really we are all stuck on an argument that is really based upon CO2 levels more than anything. CO2 levels set the desireable air and therefore nutrient temps at a maximum of the mid seventies. It has nothing really to do with DO levels or bacteria or protozoa levels when growing in a aero or hydro system. If you are running a non CO2 supplemented system then the old school opinon of air temps and reservoir temps apply, but the verbage about the reason being for increased DO or bacteria or protozoa control really has very liitle to do with it as those things are very simply addressed. And once agin if you are ragging soil or organic or immersed water growing needs into the discussion your opinion are mot to this discussion and should be discussed in a section other than aero and Hydro as they do not apply here.
Personally I keep my reservoir temps at no higher than grow room temps and no lower than grow room temps. My grow room temps are usually 85 to 90 degrees. So my reservoir temps are 75 to 80 degrees. My nutrient pumps at 25 psi and 50 to 80 micro medium pressure misters likely increase the temp a few degrees above thaose temps. I use chlorine for bacteria and protozoa control. I have no idea what my reservoir Do levels run any more as it really does not matter much. I do use a chiller as need to maintain my reservoir temps at a maximum high of what ever the room temp airconditioner thermostat is set at. I do not try to chill to below those temps. No benefit in it as my growing temps are not based upon ambient CO2 levels of 350 ppm or so..

Take It Outside: Why Outdoor Hydroponic Systems Make Sense

There are many good reasons why hydroponic gardening is typically done indoors. The heightened control of an indoor or greenhouse environment is perfect for reaping all the benefits of hydroponic growing. The advantages of hydroponic gardening generally include faster growth rates and larger yields due to the plant’s increased accessibility to nutrients and oxygen (for the roots).

Although indoor environments make it easier to control many of the variables that affect the way a hydroponic system performs, many growers are also taking hydroponic gardening outdoors. In fact, with a few alterations, most outdoor hydroponic systems will offer growers many of the same benefits as an indoor environment. Outdoor hydroponic systems also provide a possible solution for poverty stricken nations, where food security is scarce due to a lack of resources.

Advantages of Outdoor Hydroponics vs. Traditional Agriculture

Outdoor hydroponics’ largest advantage over traditional agriculture is water usage. Traditional soil-based agriculture requires nearly 300,000 gallons of water per year per person supplied with food.

For nations without a reliable source of water, traditional agriculture is either extremely limited or impossible. Traditional agriculture also requires cleared land, which reduces animal habitats and, in turn, reduces animal populations. The use of herbicides, pesticides, and fertilizers in traditional methods contribute to the pollution of land, air, and water. Not to mention this eventually sterilizes the soil, rendering it stripped of sufficient nutrients.

Conversely, an outdoor hydroponic system only requires five to 10 per cent of the water used by traditional agriculture. In other words, the amount of food produced using 300,000 gallons of water in traditional agriculture can be obtained by using only 15,000 to 30,000 gallons of water in an outdoor hydroponic system. Outdoor hydroponic systems do not require the same land clearing or destructive use of herbicides, pesticides, or fertilizers. In fact, most outdoor hydroponic systems will recycle the water and fertilizers so they can be used repeatedly.

Outdoor hydroponic systems offer another advantage over traditional agriculture in that they can be customized to fit many different applications. Outdoor hydroponic systems can be hung, stacked, set up vertically or horizontally, or configured in just about any way to best meet the needs of the space and the crop being grown.

Disadvantages of Outdoor Hydroponics

Although there are many benefits to using outdoor hydroponic systems, there are also some disadvantages. The initial cost of equipment is a large shortcoming of outdoor hydroponics. This is especially true if it is a large system and/or if the system is going to be automated. The larger the hydroponic system, the higher the initial cost. An agriculturist who has a large garden space must consider how long it will take to recoup the initial expense of the hydroponic system.

Automating a hydroponic system adds extra cost. Expensive computer controllers, sensors, pumps, and other mechanical equipment must all be purchased, synchronized, and maintained to ensure a properly running hydroponic system. All this equipment quickly adds up. However, more automation requires less labor. This can reduce costs and increase the amount of time a horticulturist gets a return on his or her investment.

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Another disadvantage of outdoor hydroponic systems is the inability to control nature. Unlike indoor hydroponic systems, horticulturists will not be able to control temperature, humidity, rain, etc. They will also not have control over lighting, since outdoor systems rely solely on the sun. Sunlight is superior to artificial lighting in many ways, but its intensity can cause problems over time for outdoor hydroponic systems.

Sunlight can cause damage to plastics and other hydroponic components that are not properly UV protected. Some hydroponic systems are more susceptible to damage caused by temperature fluctuations. Intense sunlight on reservoirs and plant modules can cause temperatures to rise and then exceed the desired temperature range for optimal growth. Modifications may have to be made to a typical hydroponic system to make the system operate as smoothly as possible in an outdoor environment.

As with traditional agriculture, regions with cold winters would not be able to grow crops year-round in an outdoor hydroponic system. Extending the growing season is one of the main reasons horticulturists choose to grow indoors or in a greenhouse.

Types of Hydroponic Systems Used Outdoors

Just about any type of hydroponic system can be used outdoors with success. That said, hydroponic systems in which the root mass is constantly submersed in water (deep water culture) are typically avoided due to the difficulty of controlling water temperature fluctuations. Top feed, flood and drain, and aeroponic systems are all commonly used with great success.

Growers will often modify these commonly used hydroponic systems when operating them outdoors. Lining the hydroponic system and reservoir with a reflective insulating material can help protect the roots from prolonged exposure to intense sunlight and/or temperature fluctuations.

Covering the hydroponic system will also help protect the plastic or other materials from being damaged by sunlight. Plants grown in an outdoor hydroponic system can grow extremely fast, which means they will take up more water and nutrients than when in an indoor environment.

Over the past ten years, three types of hydroponic systems have come into the forefront of outdoor hydroponics. Those systems are vertical hydroponic systems, aquaponic systems, and simplified hydroponics.

Vertical Systems

Vertical hydroponic systems are hydroponic systems that are set up vertically instead of horizontally. The biggest advantage of this type of system is maximization of floor space. Since the plants are set up in vertical rows, more plants can fit in a given garden area. This is the main reason why vertical hydroponic systems are utilized in rooftop gardens and in other gardens where space is limited. There are also many vertical hydroponic systems which can be integrated into urban planning and development. For example, constructing vertical hydroponic systems on the sides of buildings or other structures can be a way to produce food in densely populated areas.

Aquaponic Systems

Aquaponics is a hybrid of aquaculture (fish farming) and hydroponic gardening. Aquaponic systems use the waste produced by fish to feed the plants. Some of the most ancient “hydroponic” methods used to grow crops were essentially aquaponic outdoor hydroponic systems. The biggest advantage of outdoor aquaponic systems is the ability to produce two sources of food (fish and vegetables) from one system. Aquaponic systems also reduce the need for fertilization of the plants. In fact, in a perfectly functioning aquaponic system (with solar powered mechanical pumps), the only input would be the food for the fish.

Simplified Hydroponics

Simplified hydroponic systems are hydroponic systems being used by developing countries or in regions where access to power is impossible. Simplified hydroponics is soilless gardening without the use of mechanical equipment. In simplified hydroponic systems, the circulating or aerating of the system is done manually instead of with a mechanical pump.

The two most common types of simplified hydroponic systems in use today are flood and drain systems and floating bed-type systems. The flood and drain systems are hand-watered once or twice a day with nutrient-infused water. The run-off is collected and reused.

The floating beds are hand-aerated by stirring the water two or three times daily. The floating beds method is more susceptible to temperature fluctuations and would most likely be avoided in regions where dramatic temperature fluctuations naturally occur.

Simplified hydroponic systems offer many advantages to farmers or families in developing nations, including self-sufficiency, the ability to recycle nutrients, and reduced water usage. A simplified hydroponic system can provide about $300 worth of food for around $30 worth of nutrients. The produce grown in a simplified hydroponic system is likely to be consumed shortly after harvest, which means it will retain a higher vitamin content and will be more flavorful.

When managed correctly, a simplified hydroponic garden will provide food three to four times faster than traditional methods. Overall, simplified hydroponic gardens are a great solution for families or small communities in developing countries who seek self-sufficiency and increased access to fresh produce.

Hydroponic gardening’s role in agriculture is growing yearly. Although many outdoor agriculturists still have access to land, water, and nutrients, these resources are quickly diminishing. In terms of agriculture, outdoor hydroponic systems offer a real solution to many of the problems created by the depletion of our resources. Outdoor hydroponic systems also offer unique solutions to the problems facing urban areas and their inability to produce fruits and vegetables locally.

Don’t be surprised if, in the near future, architects include vertical rooftop systems or integrated hydroponic systems to typical building specifications. Finally, outdoor hydroponic systems are currently the best solution we have to combat many of the hunger issues facing under-developed nations.

Simplified hydroponic systems could be the difference between self-sufficiency and starvation for many families and small communities. When you examine the advantages of hydroponic gardening combined with the need for the human race to take serious steps in reducing our depletion of resources, there is no doubt that outdoor hydroponic systems will be a staple in the future of agriculture.

10 Pros and Cons Of Outdoor Hydroponic Gardening

Most people relate hobby hydroponic with growing indoors. Hydroponic is actually a great option for outdoor gardening as well. As with anything, in addition to the pros of outdoor hydroponic gardening, there are also some drawbacks to be aware of ahead of time.

Let’s take a look at some of the pros and cons of outdoor hydroponic gardening, starting with the pros.

The Pros of Outdoor Hydroponic Gardening

More room to spread out

Having a hydroponic garden outdoors gives you a lot more space compared to growing indoors. Systems can be larger and the plants can typically be grown larger as well, both making for a more abundant harvest.

Outdoor hydroponic gardening is great because you can have several different systems, growing all different kinds of fruits and vegetables at the same time, which often hard to do for indoor hobby hydroponic growers.

Moving a hydroponic garden outdoors may also make it possible for you to switch over to aquaponics, removing the need to feed your plants with liquid nutrients and providing your family with fresh fish.

The best light source

Outdoor hydroponics gives you the opportunity to use the best light source possible, the sun. There’s no need to worry about the quality or intensity as nature has you covered.

Being able to use the sun as your grow light is a huge money saver. It also allows you to use systems that may have been more difficult to provide light to indoors, such as vertical hydroponic systems or the gutter garden below that I built onto the side of my chicken coop.

Easy pollination

Pollination can be a time-consuming task when growing indoors. Looking for flowers ready for pollination, then pollinating each one by hand, coming back and repeating every couple of days just to be sure it’s well pollinated.

When your hydroponic garden is outside, pollinators such as bees will do the pollination work for you.

Easier water changes/ reuse

This pro is true for me due to where I have my indoor hydroponic garden set up. Since it’s in my garage it’s a little ways away from a water source and a drain.

I find water changes with my outdoor gardens to be easier than indoor gardens. Another benefit is that you can dilute, then reuse the old nutrient solution to water your potted plants or dirt gardens.

Lower start-up cost compared to indoors

When hydroponic gardening indoors you often need to purchase ventilation, fans, and you’ll for sure need lighting.

This is not the case with outdoor hydroponics as nature provides all of the above. For many people, it makes sense to start their hydroponic gardening hobby with outdoor growing, as it provides a low-cost way to learn more about hydroponics.

The Drawbacks of Outdoor Hydroponic Gardening

More pests

While hydroponic gardening outdoors makes pollination easier, other bugs that are harmful to your garden will also have easier access. The only way to keep bugs out is a barrier, like moving your hydroponic garden into a greenhouse. When outdoor hydroponic gardening it’s important to identify the beneficial bugs to your garden and not remove them. Allowing them to live in your hydroponic garden will give you little sidekicks in pest control.

Pests are not limited to bugs when your hydroponic garden outdoors. Many time’s I have stepped onto my back porch garden area to have several bunnies scatter from nibbling on my vining vegetables.


The heat has an effect on 2 different areas of an outdoor hydroponic system, the air temperature and the temperature of the nutrient solution. In either instance, precautions should be taken to make sure neither gets too hot.

When a nutrient solution becomes too warm it holds less oxygen, which is not only bad for the plant’s oxygen needs but sets the stage for diseases like root rot. Make sure to take steps to ensure you keep the nutrient solution cool.

When the air temperature rises, plants need to take in more water. In hydroponic gardens, to make this easier on the plants, it is a good idea to lower the strength (the EC) of the nutrient solution to the lower end of the recommended amount. Another trick to protecting your plants for the sun’s heat is to provide shading with shade cloth.

More wear and tear on the hydroponic system

The outside elements are not forgiving and put more wear and tear on the hydroponic garden as opposed to indoor conditions. Sometimes this is just apart of hydroponic gardening. In some cases you can shade parts of the hydroponic system with a tarp, keeping off the rain and protecting from harmful UV rays.

No environmental control

The lack of environmental control can be frustrating when hydroponic gardening outdoors. There are many different environmental factors that will affect your hydroponic garden.

At points, you will go through cold spells and heat spells. Wind can knock over your plants. Rain can dilute and alter the pH of your hydroponic nutrient solution.

You can also take steps to cover parts of your hydroponic system that would let in rain to protect from pH alteration and dilution. Pay attention to bad weather coming into your area and provide plants support, especially for your larger plants.

Can’t grow during the winter in many areas

In many places hydroponic gardening outdoors is not an option during the winter months, unless in a heated greenhouse. Where I live in Missouri, our winters are definitely too cold to have an outdoor hydroponic garden going.

This isn’t true of everywhere though. There are many areas where the low temperatures don’t drop much below 40 degrees, so it’s still possible to grow cool weather crops there in the winter.


There are definitely trade-offs to outdoor and indoor hydroponic gardening with each providing its own sets of benefits and drawbacks. When it comes to the pros and cons of outdoor hydroponic gardening I believe the good far out ways the drawbacks. Once you’re aware of the challenges that outdoor gardening brings, you can plan solutions ahead of time to have a smooth growing season.

What are some of the pros and cons you’ve found with outdoor hydroponic gardening? Let us know in the comments below!

Outdoor Hydroponics, Growing Without a Greenhouse

So what is the problem with the outdoors ? Well, the main problems are temperature changes, rain, haze, snow and excess light. Plants grown outside a greenhouse do not have any protection against direct sun, rain, haze or snow and are therefore most likely to be damaged by the elements. This of course, does not mean that the crops cannot be taken outside.

In countries where there are four seasons (and winter has snow), care needs to be taken not to grow any plants during the winter, because snow will most likely kill all the crops. furthermore, low temperatures are likely to freeze the nutrient solution, something that can be a really bad problem in a hydroponic garden.

Another precaution that needs to be taken is to be specially watchful of the levels of EC in the hydroponics garden. In this special case, nutrients need to added in order to compensate for dilutions caused by rain. Electrical conductivity levels need to be taken before and after a rain storm in order to know the change in EC and return it to normal after. Note that this is a special case, normally nutrients should never be added to a solution which was naturally depleted by the plants. Please read the EC FAQ post for more information about this.

Another important thing is that plants should be protected from excessive evaporation by using hydro-gels. These polymers are applied over the plants root ball and effectively retain moisture for the plant so that possible stress from excessive evaporation becomes minimal. If the sun is too strong, additional measures such as nutrient reservoir cooling (with ice for example) have to be done in order to maintain adequate temperatures around the root zone.

It is clear that hydroponic crops can be grown outside but growers have to take special precautions with this area of hydroponics and commercial growers using this technique should have the losing of one crop a year in their budget (for crops such as lettuces) due to ambient conditions ruining their growth. (below, an image from a special program done by the UN to help poor people use hydroponics as a stable source of income)

When I first became interested in hydroponic gardening I used tap water without giving it a second thought. It was only some time later when I was disappointed about the quality and health of the plants that I was growing that I looked a little deeper and discovered that untreated tap water is not the best option for hydroponic gardening.

A basic mistake, but we all have to start somewhere.

Home tap water contains a range of chemicals and minerals which can be damaging towards plants. Thankfully, there are ways to test and treat your tap water to make it safe for your plants.

Read on and I’ll tell you all you need to know about whether tap water is suitable for hydroponic growing.

The Basics

In an ideal world it would be best to start with entirely pure water when mixing a hydroponic nutrient solution. This enables you to precisely determine the exact proportion of nutrients that your plants will receive.

However, this is often impractical and expensive, but thankfully there are lots of options

What’s Actually In The Tap Water In Your Home?

I recently checked the quality of the tap water coming into my home and discovered that it is routinely tested for 82 different chemicals, minerals and bacteria. Surprisingly, my local water had failed a recent test for lead content, which was a bit concerning! Some of these chemicals cause no major issues with hydroponics, but many can significantly impact the health of your plants.

How Is Tap Water Treated By Your Water Supplier

Your local water supply may come from a variety of sources and the mineral constituents of it will depend on the geology of your surrounding area. There will also be numerous other chemicals such as copper, lead and organic material that enter the water along its journey from raindrop to the tap in your house.

Your local water treatment plant will take water directly from local water courses and treat them in a variety of ways before entering the domestic water supply.

Water Treatment

It is the job of your local water treatment works to ensure that excess levels of harmful materials are removed from the water supply to make it safe for domestic use. The first step in the water purification process is to adjust the pH of the water by mixing it with aluminium sulphate.

This is a compound which helps the impurities within the water to clump together making them easier to remove. Rapid mixing of the water maximises the amount of aggregation of the impurities within the water.

Flocculation And Sedimentation

The next step in the water purification process is for the water to be slowed down and allowed to rest in flocculation basins. This allows the aggregated impurities to come together further which will make them easier to remove.

The water is then moved into sedimentation basins and the aggregated floc is allowed to sink to the bottom of the sedimentation tank, where it is removed from the water supply.

Filtration And Disinfection

Once the larger impurities are removed from the water supply, the water is moved into filtration tanks. These tanks contain filters made from fine sand and gravel, which allow any smaller particles and microorganisms to be removed.

The water is then disinfected using small amounts of chlorine and ammonia which prevents bacterial growth in the water supply.

Things About Tap Water That Can Affect Hydroponics?

There are three main things to consider about tap water that can affect hydroponics.


Chlorine is a toxic gas, but it has many practical uses in industry and public health. Most people know that swimming pool water is chlorinated to act as a disinfectant to prevent the spread of disease. The same thing happens to tap water, but the concentration of chlorine that is used is significantly less.

Chlorinating water is a fantastic public health measure which ensures that our tap water is safe to drink. However, even at low concentrations, chlorine can be quite toxic to growing plants.

When growing plants in soil, much of the chlorine is removed by the process of the water moving through the soil. When using hydroponics, there is no soil to provide this function.

Thankfully, removing chlorine from tap water is an easy process as it is quite a volatile gas and will evaporate from the water in the presence of sunlight.

One of the most common ways of removing chlorine from tap water prior to using it in a hydroponic system is simply to leave it out in the sun for between 12 and 24 hours. This should reduce the chlorine levels in the tap water to a level that will cause no problems for your hydroponic plants.


Chloramine is a compound of ammonia and chlorine. It is made by replacing several of the hydrogen atoms in ammonia with chlorine atoms. This Is also used as a disinfectant agent for domestic tap water. It is becoming more popular as it is more effective and longer lasting than chlorine.

There are a number of significant negatives of chloramine. It can cause tap water to have an unpleasant aftertaste. It can also lead to increases in fluorocarbon and iron concentration in tap water, which can be hazardous to human health.

Chloramine can be removed from tap water by the same process as removing chlorine, but you will need to expose the tap water to sunlight for considerably longer due to the greater stability of chloramine. Another solution to remove chloramine from tap water is to use an activated carbon water filter. These are already quite common and many people choose to run their tap water through an activated carbon water filter prior to drinking it.

Dissolved Minerals (Hard And Soft Water) – Measured in PPM

As previously mentioned, the quantity of dissolved minerals in your tap water depends on the underlying rock formations that the water runs through before it reaches the water treatment works.

Rainwater is normally slightly acidic due to the reaction of water with carbon dioxide in the atmosphere. However, it does not contain very many dissolved minerals. Once the water falls to the ground it will seep into the soil and travel through soil and bedrock until it enters the waterways. During this process, mineral compounds, most commonly calcium and magnesium, from the rocks will dissolve and react with the water.

The hardness of water is measured in PPM (parts per million). This is the amount of dissolved minerals as a proportion of the water. (e.g. 100 parts dissolved minerals for every million parts water).

Soft water will have a PPM level of under about 60 PPM. Water at this level or below should cause minimal problems with hydroponic growing.

A PPM level of between 60 to 180 would be considered moderately hard, and over 180 PPM is very hard water.

Very hard water will have high quantities of dissolved minerals. The most important ones for hydroponics are the levels of magnesium and calcium.

Why Is Hard Water Bad For Hydroponic Plants?

There are a number of problems with using hard water for hydroponics.

Firstly, you will typically be using a defined concentration for your hydroponic solution. If your hard water is already at 400 PPM and the target PPM of your nutrient solution is 800 PPM, then half the concentration of your solution will be unknown minerals, which may or may not be beneficial for your plants.

Secondly, the large quantities of magnesium and calcium that are dissolved in tap water are typically too big to be of use to growing plants. These still add to the concentration of the solution and can lead to nutrient lockout. They also tend to cause aggregation with other dissolved nutrients which can affect both the pH and nutrient content of your hydroponics solution.

Thirdly, high quantities of calcium carbonate in your tap water will raise the pH of your water. For hydroponic growing, the pH should generally be between 5.5 and 7, depending on what you are trying to grow. A pH of over 7.5 will cause increasing problems.

How Chelates Can Help

Hydroponic nutrient solutions typically contain chelates to assist in making micronutrients available to the plants. There are a number of hydroponic nutrients, which are very reactive with other dissolved solids within the water.

Iron, for example, is highly likely to react with the other dissolved solids such as carbonate and phosphate, which will lead to the formation of an insoluble salt, which will precipitate out of the solution. This causes them to be unavailable to be taken up by the plant roots.

The role of chelates is to surround the reactive molecules such as iron, preventing them from reacting with other dissolved compounds, so that they remain available to be taken up by the roots of the plant.

How Can I Find Out If I have Hard Water?

The simplest way is to contact your water company and they will be able to tell you or provide you with a recent water quality report.

The second way is to purchase a TDS/pH/EC meter. This is an great device which will tell you the characteristics of the water you are using and is an important thing to own for anyone growing plants with hydroponics.

What Other Forms Of Water Can Be Used For Hydroponics?

If your tap water has a high PPM, you may want to consider alternate sources of water for your hydroponics setup.

Distilled Water

Distillation uses a process of evaporation and condensation to separate the constituents of a solution into their respective parts. In terms of water for hydroponics, it is mainly used to remove the dissolved solids within the water. It will result in extremely pure water with a negligible PPM level. You can distill water at home quite easily, although it may be more cost effective to but distilled water directly.

Reverse Osmosis Water

Reverse osmosis is a process which removes particles and dissolved solids from water by passing it through a semi-permeable membrane. Essentially, small water molecules are able to pass through the semi-permeable membrane, but larger impurities and molecules of dissolved solids will be too large to pass through the membrane. This will result in water which is dramatically purer than tap water. Reverse osmosis systems can be purchased for home use and are not excessively expensive.

Filtered Water

The simplest option is to use water which has been passed through an activated carbon filter. This will remove a lot of the dissolved solids and many, but not all of the undesirable chemicals present in the water.

How To Treat Tap Water To Make It Safe For Hydroponics

Leave the water out in sunlight for 24 hours. This will remove the vast majority of chlorine.

Run the water through an activated carbon water filter to remove the vast majority of chloramine.

Hard Water

There are three options to make hard water more suitable for hydroponics.

The first option is to purchase distilled water and dilute your own tap water to reduce the PPM to a level that is suitable for hydroponics.

The second option is to run the water through a reverse osmosis water filter. A unit can be purchased for home use that is not overly expensive and will produce water which is far more suitable for growing hydroponic plants.

The third option is to simply use a carbon based water filtration system. This will not be as effective as a reverse osmosis system and there are some limitations to the type of impurities which can be removed, but may well be sufficient for most hydroponics systems.

Coming back to the original question at the start of this article.

Can you use tap water for hydroponics?

Yes, you can indeed. You will need to test it and treat it, but in almost all situations, you should be able to use your tap water for a hydroponics system. Let me know your own experiences of using tap water with hydroponics in the comments section below.

Can I use tap water for hydroponics?

​Water is the basis for growing plants with any method, but with hydroponics it plays an even more significant role. The contents of your water before you add nutrients has a huge impact on how nutrients interact, and how your solution ultimately affects your plants.

Understanding the impact of tap water and how to reduce its negative effects will result in vigorous growth and larger yields in your hydroponic garden.

The Role of Water in Hydroponics

In a hydroponic system plants grow only in water. There is no soil or other organic surrounding that acts as a barrier for plant roots.

This means that there is a direct interaction between plants and the water they uptake, which also contains all required nutrients for growth.

Without a protective barrier to soak up excess nutrients or chemicals, if it’s in the water, it will get into your plants.

So if you’re using tap water in your hydroponics system, whatever is in your tap water will get into your plants.

Using Tap Water – What’s the Big Deal?

If you’re using tap water for hydroponics, it’s likely due to necessity, where else would you get your water from?

So you must use it, but if you understand what’s in your water, you can do a lot to control and reduce its negative impact.

What’s wrong with using tap water in hydroponic cultivation?

Chlorine and chloramines are both added by water treatment plants to kill bacteria and pathogens harmful to humans. While this is a good thing, it can be very harmful to plants.

These chemicals will kill any beneficial bacteria or fungi in your system. These microbes help to increase the amount of nutrients that plants can uptake.

Without these beneficial organisms, plants get less nutrients, therefore grow smaller and yield less

Although plants need chlorine in small amounts, tap water contains much more than plants regularly need. To add to this, many hydroponic nutrients contain chelates, which help keep nutrients suspended in water.

When chelates come into contact with chlorine, they bond and further increase the amount of chlorine taken up by plants.

Too much chlorine causes a nutrient toxicity (too much of a nutrient), which stunts plant growth.

Chelates in Hydroponic Nutrients

Chelates are used in hydroponics to help plants uptake more nutrients. Certain nutrients will not remain suspended in water, and will combine with one another to form compounds that plants can’t uptake.

Chelates remedy this issue by forming bonds with these nutrients that keep them suspended in the water, and make uptake by plants easier.

For nutrients you want getting into your plant, this is great! But certain undesirable elements in tap water are more easily absorbed by plant roots because of chelates.

When chelates come into contact with chlorine, they bond and allow more chlorine to enter your plants. This causes toxicity as it gives the plants much more chlorine than they need.

Tap water may be considered ‘hard’, which means it has a high ppm. This means that there are extra dissolved elements in the water, which can end up in your plants.

Water with a ppm (parts per million) of 150 or greater has a lot of Calcium and Magnesium in it. Although plants need both nutrients, the molecules of these elements in tap water are too large to be absorbed by roots. This means they will collect in your system and stain and clog every part of your system.

By starting with a high ppm, you have less room to add nutrients to your system. If you want to feed your plants an 800PPM solution, but have 250PPM out of the tap, you have little room left. This can make it easy to burn your plants (toxicity) or unintentionally not provide them enough nutrients.

Do you really need to be using RO water?

One of the most common practices in hydroponics is to use reverse osmosis (RO) water in order to create your hydroponic nutrient solutions. This water is made by running another water source – most commonly tap water – through a reverse osmosis system that removes a very large portion of the ions within the initial water source. The RO process is very energy intensive and also uses a large volume of water, only around one third of the water input ends up as RO water while the rest ends up as a more highly concentrated solution. Today we are going to discuss whether using RO makes the most sense, when it doesn’t and how you can make sure that using tap water does not cause you any important issues.

The idea behind using RO water is to have the best “base” for the construction of a nutrient solution. If your water starts up with some substances within it then the amount of control you have over composition is limited and therefore your results might suffer because of that. If for example your nutrients add 150 ppm of Ca but your water already contains around 40-60 ppm then adding so much Ca might place you within a suboptimal spot. If your water contains a lot of carbonates, sodium, fluorides or other substances they can also cause significant problems within your hydroponic crop. Using RO water brings a “clean slate” that ensures that what you add is what you get.

So what is wrong with RO water? There are two main issues with using RO water. The first is that it’s a very energy intensive process – therefore a costly process – and the second is that the waste products of the RO process can create environmental problems. Additionally tap water already contains many nutrients necessary for plant life – mainly Mg and Ca – so why would you remove these elements only to later add them again later on? Surely you would rather save the energy from the RO process and use the nutrients within your water as part of your nutrient solution.

The above map shows you the mean hardness of water (as ppm of calcium carbonate) across the United States. The people with the highest Ca concentrations have around 100ppm of Ca while those who have the least have around 0 to 24ppm. This means that for the people with the highest Ca, the Ca from tap water could contribute more than 50% of the Ca needed by a flowering crop while for the other states the contribution would be rather small. If your water is high in Ca then chances are it is also high in Mg so performing a water analysis will be necessary. From my experience with customers Mg is usually around one fourth to one third the concentration of Ca in solution, but the proportion can change significantly depending on the zip code. The table below shows the Ca/Mg content of water sources at different overall hardness levels in Germany.

Mineral content in water also changes substantially as a function of temperature since rocks that contribute Ca/Mg carbonates will be more soluble during the warmer months of the year. It is therefore ideal to get two analysis, one during February – usually the coldest month – and another during August, the hottest month, to get a good idea of the range of Ca/Mg concentrations that you will be getting in your tap water. This will allow you figure out how to adjust your nutrients as a function of the average temperature where you live.

Carbonates are also something you should worry about, if you have a high water hardness you might have more than 150ppm of carbonate within your nutrient solution. This is not ideal since carbonate ions can cause issues in your crop. To deal with this you can simply work at a slightly more acidic pH (say 5.6-5.8) this will limit the amount of hydrogen carbonate ions that can be present within the water as it will shift the equilibrium significantly more towards the evolution of carbon dioxide (since carbonic acid in solution is in constant equilibrium with atmospheric carbon dioxide).

There are however some circumstances where using RO water is unavoidable. If you water contains more sodium than your crop can deal with (read here for more info), more than 50 ppm of chlorides or if there are more than 10 ppm of fluoride then you will need to use RO water because those elements in those quantities are not going to be good for your plants. If these elements are absent or in low enough quantities then there is no reason why you would want to use RO instead of tap as using RO would be an unnecessary energetic and environmental expense given that you can just compensate for the ions already within your water through adjustments in your nutrient solution.

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