Water Worker 4.4 Gallon Water Heater Expansion Tank is a diaphragm-type pre-pressurized expansion tank designed specifically for potable hot water systems. It effectively controls water pressure build-up and eliminates relief valve spillage caused by thermal expansion when water is heated. Featuring a 3/4" male pipe thread connection, this tank requires no maintenance and meets code requirements in many counties and states. It is compatible with models G5, G5L, G12, and G12L, with a maximum allowable working temperature of 200°F. The standard factory precharge is set at 40 PSIG, while the relief valve must be set at 150 PSIG, ensuring the maximum pressure is maintained at least 10% below the relief valve setting. This model is listed with IAPMO and SBCCI and is NSF listed for the liner only, ing high standards of quality and safety. Model Number: G12L