Ma'anar ƙamus na "ruwa mai laushi" yana nufin ruwa wanda ke da ƙarancin narkar da ma'adanai, musamman calcium da magnesium ions. An fi son irin wannan nau'in ruwa sau da yawa don amfanin gida, saboda ba shi da yuwuwar barin ma'adinan ma'adinai ko haifar da tarin bututu da kayan aiki. Ana samun ruwa mai laushi ta hanyar matakai irin su reverse osmosis, ion exchange, ko distillation, kuma sau da yawa ana bambanta da "ruwa mai wuya," wanda ya ƙunshi manyan matakan narkar da ma'adanai.