Water is the only transportation source for the nutrients and other additives to get to the root system of the plants. So the water supply quality is an important factor to consider for plants grown hydroponically. Plants are more sensitive to certain water treatments than people are, so there are often things left in the “Safe Drinking Water” that are a problem for your hydroponic plants. Not all water is created equal, tap water, reverse osmosis (RO), distilled, rainwater, well water, lake/pond and even stream water all have their advantages and disadvantages.
Problems with Tap and City Water
The municipal city water supply standards for drinking water vary from place to place. These often have chemicals added to bring them up to drinking standards. These drinking water standards apply to making water safe for people to drink, but not necessarily safe for hydroponics. Salt (sodium chloride) may also be in the water supply. Sodium is toxic to plants and even in small amounts can accumulate in recirculating hydroponic systems, causing major growth problems.
City water often use chlorination to control bacteria levels. Fortunately chlorine will dissipate quite rapidly, and you can usually smell high levels of chlorine. This can be taken care of by placing the water in a open aerated holding tank and allowing 2 to 3 days for the chlorine to dissipate before mixing up the nutrient solution. City water may also contain herbicides, these can be very damaging to hydroponic plants. Carbon filtration will be able to remove most of these contaminates, as long as the filter is changed often enough.
Usable plant elements like Nitrate, Magnesium, Potassium, sulphur, Boron, Copper, Manganese and Zinc can all be present in most water sources. Hydroponic nutrient manufactures take this into account when manufacturing them. But these can all be present in different amounts, and/or not at all, this will effect the overall composition if the nutrient solution, and thus the plants growth. The only way to have the perfect nutrient solution is to have the water tested and a nutrient solution made specifically for your plants and water supply combined.
Problems with Pond, Lake, Stream and Rain Water
Well water, lake water, pond and stream water, may all likely have bacteria and soil-born pathogens in them that are not good for your hydroponic plants. They can cause a variety of diseases to your plants, and can be difficult to get rid of. Chlorination as a water treatment is probably the most common form of treatment, although you will need to all the chlorine to dissipate before use. Hydrogen Peroxide is also effective as a sterilization procedure, but should be allowed to dissipate before use. Hydrogen Peroxide in larger amounts can also be damaging for plants. Although in smaller quantity’s like 1 teaspoon (5ml) per gallon of water can actually be beneficial to the plants, by adding extra dissolved oxygen into the nutrient solution. Beneficial microbes can also help in suppressing the unwanted plant pathogens, because they feed on the unwanted ones.
Rain water (depending on how and where it’s collected and stored) may contain contaminants also. Areas with high pollution regularly produce acid rain, this is a result of the raindrops collecting and holding onto the pollution on it’s way from the clouds to the ground. Rainwater collected from a galvanized iron roof and/or rain gutters may contain high levels of zinc. Water stored in new cement tanks may have minerals in it that have leached into it from the cement. Rainwater should be tested to check for possible problems.
Reverse Osmosis (RO), Distilled and Water Softener Water
A lot of water sources are considered hard water. Hard water can cause multiple problems, besides the added minerals. High levels of iron, calcium, lime scale and other elements when they make contact with solid objects like pumps, tubing, heating elements and drip emitters, it will begin to scale up. This causes many problems with things clogging, stop working, it can even cause pH problems.
Hard water can be cleaned using water softeners that use a ionizing resin that back flushes through salt. Although this process adds a small amount of sodium (salt) to the water which is toxic to plants, and as it builds up can be a big problem. Smaller computerized water conditioning units that are designed to prevent scaling for home use, would be better in the long run. Reverse Osmosis (RO) systems will be able to take out the contaminants without adding sodium to the water, however most RO systems designed for the home only produce a gallon or two per hour. Though there are RO systems that can provide 100-200, and even 700 gallons per day. Depending on the RO system, filter changes, RO systems may be able to provide a almost distilled water quality.
Distilled is truly pure water and free from any bacteria and pathogens, but it’s also free of all trace elements that pre-manufactured nutrient solutions have expected to be in the water, so they have compensated for that. Clean pure water will give your hydroponic plants the best start in being healthy from the beginning, and even when using a better quality water source when problems have been noticed can results in significant improvements in the plants health, and growth.