The fact that you don’t need soil for your hydroponic garden does not mean that you can use any kind of water to grow your garden hydroponically. Water quality is very important for great results in hydroponic gardening and there are certain factors that you should consider before determining what kind of water is best for hydroponics gardening in your location.

Importance of Water in Hydroponics and the Best Type of Water for Hydroponics

Water is the main medium of plant sustenance in hydroponics gardening or farming. The nutrients that plants need to grow and survive are dissolved in water and plants get to absorb them from the water.

The fact that a water source is clean and pure does not mean it is the best water for hydroponics use. Plants have unique needs and nutritional requirements using any type of water for hydroponics without first testing it may be detrimental to plant health.  

There are many factors that tend to affect water quality but the best type of water for hydroponics should be derived from pure water sources that do not have contaminants or elements that can interfere with plant nutrition.  

Different Types of Water for Hydroponics

There are different types of water that can be used for hydroponics and each type of water has its pros and cons. See the various kinds of water that can be used for hydroponics gardening or farming, the advantages and disadvantages of using it, and the solutions that can be implemented to make the water safe for hydroponic use.

Tap Water for Hydroponic Use

Tap water is the most commonly used type of water for hydroponics especially for people living or farming in urban areas. People living in these areas may be forced to depend on the city water supply since there may be city ordinances or laws preventing them from drilling boreholes for their own private water supply.

Urban or municipal water supply is usually very clean and safe for consumption but may not be safe for plants or use for hydroponics. This water is normally treated with chlorine and other chemicals before distribution to homes. However, plants only need chlorine in trace amounts so the amount of chlorine in tap water may be at unsafe levels for plant health.

Solution: Tap water from city or municipal water supply can be made safe for hydroponic use by simply leaving the water in the reservoir open to air and aerating it for 48 – 72 hours so that the chlorine in it can evaporate away. Try to ensure that the chlorine content is less than 1PPM before you can use it for mixing hydroponic nutrients for plants.

Most city water supplies are now treated with chloramines. Chloramines are chemical compounds created from chlorine and ammonia reaction. It can be removed from tap water by doing reverse osmosis with a reverse osmosis system or machine. 

Rain Water for Hydroponic Use

Rainwater may seem to be the best type of water for hydroponic use because of how pure it can be. However, there are a number of issues that may make rainwater bad for hydroponic use. It is very likely that rainwater can be contaminated and result in acid rain if you live in an area with a high level of atmospheric pollution (air pollution) with acid anhydride gases. This type of rainwater can be unsafe for hydroponic use.

Also, the vessels for rain water collection may contain or produce contaminants that can alter the quality of water. For instance, rain water collected from roofing sheets or roof gutters are likely to be contaminated with zinc from galvanized iron roofing sheets. Also, hard elements like magnesium, calcium can leach into rain water stored in storage reservoirs made from concrete. This can make the water become hard or increase the electrical conductivity of water, making it unsafe for use as a hydroponic nutrient solvent.

Solution: Rain water is very unlikely to have a lot of contaminants but you should test it to know its quality first before deciding on whether to treat it or not. There are two potential ways to treat contaminated rain water to make it safe for hydroponic use.

1. Water softener: This can be used if the rainwater test shows significant amounts of hard water elements. This should be done carefully and minimally since water softeners can also affect the electrical conductivity.
2. Reverse Osmosis (R.O): Reverse Osmosis can be used for treating contaminated rainwater. The water is filtered through R.O machines and the contaminants are removed in the process. The disadvantage with this method is that it can be expensive and may quickly drive up costs.

Well Water for Hydroponic Use

Ideally, well water may not be suitable for hydroponics because it contains compounds of calcium, magnesium, etc. that may make the water highly alkaline. Well, water is also very likely to have disease pathogens that may infect plants.

Removing hardness from well water using chemical agents can introduce other chemical compounds in the hydroponic nutrient solution after removing the compounds causing water hardness. This may prevent plants from obtaining the required nutrients from the solution.

Similarly, most disease pathogens in water can be eliminated through water chlorination but this also means that additional chemicals i.e. chlorine will cause the development of chemical compounds that may prevent plants from absorbing the nutrients needed for growth and development.

Solution: The simplest method of treating water hardness is by boiling the well water and filtering out the scum of precipitates of calcium and magnesium compounds responsible for the hardness. However, this can only be effective for small scale hydroponic gardening especially if you are doing it as a hobby.

The best method of treating well water hardness is through a process known as reverse osmosis (R.O). The process involves passing hard water through several membranes and filters to remove the chemical compounds causing water hardness. This is usually done by machines specially designed for this purpose.

The disadvantage of this process is that it can be expensive and it can quickly increase your production costs. This is one of the reasons why well water should not be the main source of water supply for hydroponic use.

Distilled Water for Hydroponic Use

One question people always ask is “do I need to use distilled water for hydroponics?” The short answer is No. You don’t have to use distilled or purified water for hydroponics, you can always use other types of water for this purpose.

However, purified or distilled water is best for hydroponics when you want to ensure that there is no interference in the availability and absorption of plant nutrients. Purified water does not contain any chemical compounds that may interact with plant nutrients in hydroponic solutions which normally results in decrease in available nutrients or creation of other compounds that may affect absorption of nutrients.

In as much as purified or distilled water is good for hydroponic gardening, it is important to monitor the water PH closely. This is because the pure water can react with carbon dioxide to form weak acids which tend to lower the water pH.

Another disadvantage with using purified or distilled water is that it can be expensive to distill water or purchase purified water for use on a large scale except if you are only doing it on a small scale or as a hobby.

Solution: It is important to monitor the water pH before mixing plant nutrients and to monitor the pH periodically to ensure that the pH is stable. You can add hydroponic pH stabilizers to keep the pH levels stable whenever there are significant or extreme changes in water pH from the neutral pH.   

Spring Water for Hydroponic Use

Most people who live close to water springs or have access to this source of water always ask this question – “Is spring water good for hydroponics?” Springwater may not be good for hydroponics because of chemical substances that may be dissolved in it or other contaminants that may have adverse effects on plant nutrition.

It is important to check for properties like pH of spring water, electrical conductivity, or PPM to determine if this source of water will be good for hydroponic use.

Solution: There is no additional value or unique advantage in using spring water for hydroponics and the cost of filtering or purifying it before use can be quite high in some instances. It is often better to consider using cheaper sources of water for hydroponics with better advantages except if you don’t have any other options.

Considerations for the Best Water for Hydroponics Use

There certain key factors that must be considered when thinking of the best water for hydroponics use. Analyzing these factors can help you to determine the water source that will likely result in the best yields and outputs for your plants. Some of these factors include:  

• Availability: Which water source is easily available and cheaper for you to use, and how much treatment are you likely to do for this water source to make it suitable for use?

• Cost of Treatment: How much will it cost to treat the water source to make it safe for hydroponic use? You need to determine the cost and if you are willing to spend that much as well as if there is a better alternative. Decisions around cost are very important if you are doing hydroponic farming on a large scale commercial level because it enables you to determine how sustainable and profitable your hydroponic farm can be in the long run. This is important because water purification methods like reverse osmosis can be very expensive.

• Risk Evaluation: You also need to consider the risk of using any water source and what kind of impact it will have on your farm or garden. For instance, what will be the impact of a disease outbreak on your plants if you decide to use water from stream or open well? What measures are you willing to put in place to mitigate or prevent these risks? What will be the impact of water treatment equipment failure on your farm or garden and what contingency measures will put in place should this risks occur?