The 2" Watts 909 HW Series Reduced Pressure Zone Assemblies were manufactured from 1979 and are still currently in production. The 909 HW is the hot water version of the Series 909 and can handle temperatures up to 210F. The 909 HW is a bronze bodied device. It features two check covers and a seperate relief vlave cover. Check valves are self contained and the relief valve is a stem type. In 2010, the LF909 was introduced to comply with the new "Lead Free" laws. All repair parts were converted to lead free in 2013. Lead free repair parts will fit both regular 909 and lead free LF909 models. All 909 models have replaceable seats and require no special tools for repair.