Softening is recommended when hardness of water is more than:: (A) 50mg/litre, (B) 75mg/litre, (C) 100mg/litre, (D) 150mg/litre
Answer is D. Softening is recommended when hardness of water is more than 150 mg/L (> 3mEq/ L). Softening of water is done by Temporary hardness Permanent hardness Boiling Lime NaCo3 Permutit NaC03 Base exchange