Add Salt Regularly. the amount of salt required can differ from system to system, and this information can ordinarily be found in the owner manual. However, as a general rule salt should be added if the level is under half-full. 3. Know What Kind of Salt to Add. Your water softener will use one of three types of salt: Tablet, Granular, Block. In the majority of cases, this will be determined by the water softener manufacturer, and again, guidelines should be provided in the user manual. However, tablet salt is generally the most common type of salt used, because it dissolves most easily and won’t build up sediment in the brine tank.