A water quality index that describes the concentration of alkaline salts in water, mainly calcium and magnesium. If water is “hard” then more soap, detergent or shampoo is necessary to make bubbles for effective washing/ cleaning. Hardness is measured in milligrams per liter (mg/l) but may also be reported in the archaic form of grains per gallon. [One grain of hardness equals 17.1mgl] Typical water hardness classifications are:
- Soft water less than 17mg/l
- Slightly hard 17- 60 mg/l
- Moderately hard 60-120 mg/l
- Hard 120-180 mg/l
- Very hard 180 + mg/l
