If water contains dissolved calcium hydrogen carbonate, out of soaps and synthetic detergents which one will you use for cleaning clothes ?
Calcium hydrogen carbonate reacts with soap to form insoluble compound. It reduces the cleaning capacity of the soap.
3RCOONaSoap+Ca(HCO3)2⟶(RCOO)2(ppt)Ca↓+2NaHCO3
Synthetic detergents do not form such compounds so they can be used for cleaning clothes with water containing dissolved Ca(HCO3)2.