The permissible limit of hardness of water fore low pressure boiler is _____________________?
A. 30 mg/litre
B. 40 mg/litre
C. 50 mg/litre
D. 60 mg/litre
A. 30 mg/litre
B. 40 mg/litre
C. 50 mg/litre
D. 60 mg/litre