Water quality: The key to optimum management in hydroponic systems 

The water source used as a base for nutrient recipes should always be evaluated. The quality of water source can really affect your hydroponic production and your system management across the crop cycle.

Is important to test your water before starting any hydroponics project in order to know if anything must be fixed before running your project.

Most of the time water for hydroponic projects comes from public utility, wells or rain. Each of these options can present different characteristics:

Municipal water: This type of water is distinguished for the presence of chlorine. Is common to use municipal water in small projects However, due to the cost, this is not the first option for big growers. Municipal water is treated with chemicals such as chlorine to avoid illness in people due to the presence of different microbes. Chlorine can affect water pH and damage sensible crops. Is good to know Chlorine can be removed from water before adding nutrients.

Water form wells: This type of water can be high in some minerals like Carbonates. In addition, water from wells does not have any previous treatments, meaning pathogens with potential to make your crop sick, can be present. There are also good laboratory tests you can use to test your water for any potential pathogens affecting humans or plants.

Rain water: This type of water can have great quality, is free of additives and has low mineral content. Usually only in places closer to the sea, sodium may be in high quantities. However, depending where you are located and the climate present, collecting the amount of water necessary to run a hydroponic system can be a challenge.

Surface water: Surface water refers to the water coming from rivers, lakes or canals. Quality between these water sources can be really different. Some places can be more saline than others. You must also take care of pathogens mostly when the water source is closed to urban or horticultural areas.

How to evaluate water test results?

When testing a water source you should always focus on: Chlorine, Alkalinity, Minerals, Bacteria, EC and pH.

Chlorine: Is mostly present in high concentrations in municipal water. Chlorine in high quantities can damage sensible crops such as lettuce and strawberry. Chlorine levels in your water source should be always maintained under 70 ppm. If your levels are higher, reverse osmosis with an active carbon filter can be used to efficiently remove any chlorine excess. There are also evaporation methods to get rid of chlorine in our water source. 

Bacteria and pathogens: Is important to know how “clean” your water is. Water sources can contain pathogens with the potential to introduce diseases to your crop. If you know there are horticultural areas close to your source of water you must then understand the risk of disease will be higher. 

Minerals: Minerals such as Mg, K, S  and N can be good for plants. But high quantities of these nutrients can cause trouble. If any of these minerals are in excess on your source of water you can fix this by adjusting your nutrient formula. We will be learning how to do this in the fertilizer management section of this guide. 

Alkalinity: Alkalinity is also mineral related but mainly focused on carbonates. Carbonates sometimes can be high in water from walls or rivers. The higher carbonate content the higher pH on the water source. This variable can really affect your system management across the cycle. Therefore it is recommended to eliminate carbonates before using the water in your system. In order to reduce or eliminate carbonates a pre-treatment of acid can be used. Also ammonium based fertilizers can be a good option to reduce pH levels in your system. Ammonium based fertilizers tend to acidify the rootzone and nitrate based fertilizers tend to increase pH. This is also good information that we should check when applying fertilizers.

Electrical conductivity (EC): EC is directly related to the amount of salts present in the water source. Remember when making a nutrient solution you will be adding fertilizer to the source of water which will increase EC levels. If the water source is high, then after adding the amount of fertilizers recommended for a particular crop you can end up with an EC level above the recommendations. Is important to start a system where the water source EC is low. In close systems we recommend to start with a water source with an EC of 2.5 mS or less. Same recommendation can be applied to any system where a crop sensitive to salts is grown. A great example are strawberries. How can we correct high EC levels? We can use filters or reverse osmosis in order to reduce salts present in the water source.    

pH: This variable will be the result of presence of different salts on the water source. All crops have specific pH requirements, mostly going from 5.4 to 7, therefore in order to keep pH in good levels it is recommended to check our water source is between 5.4 and 7 (crop specific). If pH is not within the recommended range nutrient uptake can be affected and nutrient deficiencies can take place. 

Here you will find a good example for a water source test:

Hort Americas offers the educational resources required in order to learn how to adjust your nutrient recipe based on your water source. Check out our Fertilizer Management guide and short course