Page 103 - Pharmaceutical Analytical Chemistry III

Classification of water :

Waters are commonly classified in terms of the degree
of hardness.
(1 Degree = 1 mg CaCO3/l) :

(1) Soft water : 0-75 ppm or (mg/l)

(2) Moderately hard water : 75-150 ppm

(3) Hard water : 150-300 ppm

(4) Very hard water : 300 ppm or more