NR701 Non-Return Valves combine the mandatory functions of isolating valve and non-return valve for the installation of pressurised water heaters. They prevent the backflow of water from a water heater to the mains line. This serves the dual purpose of protecting the mains supply from contamination, and the loss of water that has already been heated. MATERIALS: Body - Cast gunmetal Internal Parts - Brass and stainless steel Seat Disc - Nitrile