A mechanical element + polyphosphate salts. A filtering element of the cold water ensures water purification from mechanical impurities, rust, precipitation. The filtering element contains polyphosphate salts, which, reacting with calcium dissolved in water, modifies the chemical formula of lime and softens water, preventing household appliances from scale formation.Maximum water temperature: 38°C. This is the best water filter for your washing-machine, water boiler or any water heating appliance. Not recommended for drinking water.