Amtrol 141N43 Therm-X-Trol ST-12 Expansion TankAMTROL ST-12 (Therm-X-Trol) is a water heater expansion tank, designed for use in domestic hot water heating systems to eliminate the potential hazards of water expansion. Water heater expansion tank is commonly installed in a domestic hot water system that contains a backflow preventer, a check valve or a pressure reducing valve. AMTROL ST-12 Applications: Residential water heaters, Laundromats, dormitories, office/apartment buildings, restaurants, etc.Eliminates the waste of energy and water, thus saving moneyProtects the water heater and plumbing fixtures from premature failurePrevents a dangerous pressure build-up in the systemPrevents the relief valve from going offTherm-X-Trol brand is the #1 choice of professional installersA professional plumber should check the complete system, including the Therm-X-Trol, yearly and more frequently as the system agesDimensionsProduct Depth (in.)11 inProduct Height (in.)15 inProduct Width (in.)9 inDetailsFinish FamilyWhiteNominal Tank Capacity (gallons)4 galPack Size1Product Weight (lb.)11 lbAdditional ResourcesFrom the ManufacturerWarrantySpecificationProduct BrochureUse and Care ManualInstructions / Assembly