Understanding Water Hardness

Jeremy Compton, North Jersey Tree Fruit Technician

Win Cowgill, Area Fruit Agent

Over the past few weeks we have discussed the issue of water hardness, and how it can effect the performance of certain Plant Growth Regulating products. Hard water not only affects the performance of these products, but it can have an effect on the performance of many pesticides, including herbicides and nutrient sprays. Understanding this, the question remains as to what constitutes hard water? It’s commonly understood that water hardness is related to the amount of dissolved calcium carbonate in the water supply and is the cause of soap scum and clogged pipes. But, the influence of other factors and concentration of dissolved minerals in the water supply needed to create hard water are rarely questioned.

Hard water is a very common problem that affects more than 85% of the national water supply. The presence of dissolved carbonates, sulfates, chlorides of calcium, magnesium and iron in the water supply cause it. Calcium hardness is the amount of dissolved calcium (plus other minerals such as magnesium) in the water. Though hard water may be detrimental to pesticide activity, it does not affect human health. Water hardness is measured in parts per million (ppm) or grains per gallon (GPG). A GPG is equivalent to 17.1 ppm. Water is considered hard when it measures 250 ppm or 14.6 GPG. Also, its alkalinity (total amount of alkaline materials in the water) must be over 150 ppm in order to be considered hard. Soft water contains less than 50 ppm (3 GPG) of calcium carbonate and an alkalinity of under 30 ppm.

If you suspect that you have hard water, it can easily be tested. There are cheap and simple methods available to growers. Contact your county agent for sampling instructions and procedures.

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