<prompt> Softening is recommended when hardness of water is more than:50mglitre75mglitre100mglitre150mglitre  <response>: Softening is recommended when hardness of water is more than 150 mgL 3mEq L. Softening of water is done by Temporary hardness Permanent hardness Boiling Lime NaCo3 Permutit NaC03 Base exchange 