What is hard water? Hard water is that which has a high concentration of the mineral salts calcium and magnesium, also called “limescale”. The formation of limescale is a problem for our plants and our plants roots.Calcium phosphate is what our bones are made of and it is 95% water insoluble. The calcium phosphate often falls out of the nutrient solution as lime scale. Once lime scale is formed both the calcium and phosphorus become unavailable to the plant.

We can use our EC meter to measure the total quantity of dissolved mineral salts in our water but that still will not tell us what percentage of those salts are hard water minerals. 

 To compensate for excess minerals, hard water nutrient formulas are usually lower in calcium and magnesium, with reduced levels of sulfates, so a hard water nutrient formula complements the minerals already present in the water. 

Also, if water is excessively hard, or an analysis shows  toxic levels of trace elements such as sodium or boron, the water should be filtered or processed.

HOWEVER, most growers will simplify water quality management by using only reverse osmosis water. RO removes all (90-95%) of the mineral ions, so the grower starts with clean, pure water. Therefore, if you use RO water all of the essential elements will come from your nutrient solution, not from the source water, creating the perfect mineral balance for plant growth. 

RO is definitely recommended for any applications where a water softener is in place. A water softener does not remove the calcium and magnesium from the hard water, rather is replaces them with sodium ions, often at toxic levels. If sodium exceeds 50ppm the plants may not be able to reach their true genetic potential. 

RO water is also perfect for topping off your reservoir between nutrient changes, replacing water lost to evaporation without adding any unwanted minerals.

Experts say that if an analysis shows that even one element is approaching toxic levels an RO system is definitely needed.