The WaterSentinel® Scale and Lime Guard has a unique formula that eliminates scale and lime build-up on your dishwasher's heating element, helping it to run like brand new. It also prevents deposits on dishes during the rinse cycle, so they come out sparkly clean every time. Just hang the Scale and Lime Guard in your dishwasher and leave it for up to six months. Once in contact with water, the WaterSentinel® releases food grade polyphosphate, stopping scale and lime in their tracks. USA.