National Standard Plumbing code 10.5.7 requires backflow prevention to prevent backflow into the main water. However, the installation of Back Flow Preventer as well as Pressure Reducing Valve (PRV) and Check Valve can close the water system. Closed plumbing system can leave no room for the possible expansion. When the water is heated during non-use periods, thermal expansion can occur. It can damage the water heater connections, gas water heater flue tubes, pumps serving washers and dishwashers, leaking faucets, ˝weeping˝ of water through the water heater T&P Relief Valve, and noisy water hammer in the pipes.


A.O. Smith PMC-10 Expansion Tank can eliminate these problems of residential and commercial water heaters as it can give water a place to go when thermal expansion occurs. Once the water heating cycle ends, or when any fixture is opened within the system, the impact of thermal expansion will be reduced so expansion tanks adjust its air pressure to match the inlet water pressure. Lastly, the water will drain out of the expansion tank to return into the system.

  • Potable Expansion Tank
  • Non-corrosive metal air valve
  • Powder-coated interior and fittings
  • Electrostatically applied powder coated exterior
  • Durable butyl rubber parabolic diaphragm
  • Positive lock retention system
  • Field-adjustable 38 PSI air charge
  • Multiple head construction
  • No-weld steel base
  • IAPMO Approved
  • 5-year limited warranty


  • Max water pressure: 150 PSI
  • Max temperature: 140°F Residential / 180°F Commercial
  • Tank volume: 9.21 Gal
  • Max acceptance volume: 5.25 PSI
  • Conn. size: ¾ NPT
  • Dimensions (D x H): 15 3/8” x 15 1/2”
  • Weight: 20 lbs
  • Heater size: up to 120 gal