The aqua-Dial Combi-Care Compact is designed to reduce the build up caused by hard water. It works by proportionally blending a minute amount of aquablend Polyphosphate into the water. The Aquablend suspends the hardness salts thus preventing them from forming scale. Storage tanks and cylinders can be treated and they can also be used with the same cartridges in soft water as a corrosion inhibitor. For whole house, hot water systems and/or individual appliance protection. A permanent treatment preventing hard water scale and soft water corrosion problems. Fits horizontal or vertical pipework. Flow rate up to 54ltrs/min (22mm) 12 months cartridge life. Free annual reminder system. Works on high or low flow rates. Unless hard water in your heating system is treated, scale builds up .