Guar has U.S. Public Health Service approval in potable water treatment as a coagulant aid together with alum, ferric sulfate, and lime. Guar increased the size of the flocinitially formed by the coagulant, thereby increasing the rate of settling of solid impurities, reducing solids carry over to the filters, and increasing periods between back-washes. In industrial waters, guar flocculates clays, carbonates, hydroxides and silica when used alone or in conjunction with inorganic coagulants.