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ASK ERIK - Can I use tap water in hydro or do I need RO water?

Erik Biksa is respected throughout the world Erik Biksa is respected throughout the world

I heard you were at Rosebud Magazine now. Glad to see it. I have been reading your column for a long time and have enjoyed learning more from your “Hydroponics Secrets” videos. Where I live, in Vancouver, B.C., the water seems to be of good quality for drinking; it’s around 30 PPM coming out of the tap. There is a lot of talk these days about using RO-treated water in hydroponics. I grow in soil and with hydroponic systems. Can I use tap water, or do I have to use RO-purified water to get good yields and avoid problems?

Erik BiksaErik BiksaI’m happy you have been finding some of my other grow-related features informative as well.

By most standards, 30 PPM (parts per million) in TDS (total dissolved solids) would be considered good-quality water. However, this measurement is just the tip of the iceberg. For the best results in your garden, there are other factors to consider in assessing water quality.

Most people are aware of the harmful effects that chlorinated water can have on the beneficial microbial life that lives in a healthy root zone. As you may know, there are liquid beneficial bacteria or beneficial fungi formulas that you can add to your root zone in your hydroponic system to enhance, protect, and supercharge your roots. But if your water is chlorinated, it can kill those beneficials!

Regular chlorine can be removed from water by aerating it overnight before adding your beneficials. Unfortunately, some municipalities use chloramines, which is chlorine altered on a molecular level to make it more persistent. This cannot be as easily removed and can cause serious problems in the garden.

Other unseen potential dangers can lurk in the water supply. Some of them emanate from the source water, and others are added to the source water by all the miles of different types of piping it takes to deliver it out of your tap. Heavy metals like mercury and lead may occur; these are easily absorbed by most types of plants. Fluoride is another potential problem, although less is known about its effect on plants and what happens when people consume them. In some regions, E. coli outbreaks have been traced to water sources. If you were to spray your plants with contaminated water and then consume them, there is potential for health risk.

The short answer is no, you don’t have to use RO (reverse osmosis) water to grow good crops based on the relative purity of the water available to you. In other regions, growers are not so fortunate; their tap water may be very high in dissolved solids—for example,  over 250 PPM.

In terms of simple nutrient chemistry, if your tap water is over 150 PPM in TDS, you should RO-filter your water to avoid any potential lockouts of nutrients.

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This rule does not account for the other issues mentioned here; for example, chloramines, heavy metals, and other potential contaminants. Historically, most growing literature has not looked beyond common naturally occurring dissolved solids in natural water sources; for example, magnesium and calcium carbonates. We live in a day and age in which water supplies are more vulnerable to man-made contaminants that can have an ill effect on the health of living organisms.

Healthy water makes for healthier plants and people. Therefore, it is recommended that you use RO-filtered water for performance gardens. If you have invested a significant amount of time and money in your indoor crop, you will want to maximize your returns. For the benefits that RO filtration offers, it is a relatively small investment for most gardeners.

Outdoor growers using chlorinated water supplies are harming the beneficial life that naturally occurs or that may be added to the soil. Beneficial microbes are very important to the health of the soil, which in turn dictates the potential health of the plants.

RO filtering should give you water that is near zero PPM and will remove almost all the other harmful impurities common to water sources. RO-treated water is very pure and highly reactive. It’s a good idea to stabilize RO-treated water with a hydroponic calcium and magnesium supplement (150 PPM) before adding your other nutrients or beneficial microorganisms. This does not at all defeat the benefits of applying RO-treated water. Calcium-magnesium supplements formulated for hydroponics contain elements in plant-available forms and will not have adverse reactions with your nutrients, the way calcium and magnesium carbonate will (as found in water supplies). Essentially, the grower is creating “remineralized” water that is free of harmful contaminants and unwanted impurities. You and your plants can then drink to bigger yields.

Erik Biksa

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Erik Biksa's series of videos on YouTube is called Hydroponics Secrets
Last modified on Friday, 19 October 2012 13:59

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