Amtrol® THERM-X-TROL® 143-327 ST-30VC Diaphragm Thermal Expansion Tank, 14 gal Capacity, 0.64 Acceptance, 150 psi Pressure, Heavy Duty Butyl Diaphragm, 16 in Dia x 19 in H

  • Acceptance Factor: 0.64
  • Capacity: 14 gal
  • Country of Origin: US
  • Diameter: 16 in
  • Domestic/Import: Domestic
  • Finish: Red Oxide Primer
  • Height: 19 in
  • Manufacturer Name: Amtrol
  • Material: Steel Shell
  • Pressure Rating: 150 psi
  • Series: ST-30VC
  • Temperature Rating: 200 deg F
The THERM-X-TROL is designed to provide control of maximum system pressures at a level below the relief valve setting. It also provides an additional space in the system to accommodate the increased volume of water created by thermal expansion, returning it to the system when hot water delivery is demanded. Maximum pressure is kept well below the relief valve setting by the THERM-X-TROL, with its pre-charged air cushion that is separated from system water. The relief valve does not open, therefore "spillage" is eliminated.
  • Features and More


  • Broadest line of sizes and models (37 models, ASME code and non code)
  • Water heater and fixtures are protected
  • Eliminates BTU and water waste, saving money and energy
  • No dangerous pressure build-up in the system
  • Relief valves will not be triggered
  • Potential safety hazard reduced
  • Accepts expanded water caused by thermal expansion
  • Returns water to the system when hot water is used
  • Protects water heater and fixtures
  • Full and partial acceptance bladders are replaceable
  • Diaphragm models include Clean Water Technology™
  • Deep drawn domes vs head and shell construction
  • Smaller weld area eliminates potential leak paths
  • Reduced diameter allows tank to fit a tighter footprint
  • Lighter weight makes handling easier
  • NPTM connection simplifies installation
  • More convenient air valve location
  • Fixed diaphragm construction
  • Seismic restraints available on stand models only
  • 3/4 in NPTF stainless steel system connection


  • Closed potable water systems to control pressure build-up


  • ANSI/NSF61
  • Division 1 Standards
  • IAPMO Listed
  • NAF 2016 Compliant


  • 1 Year Limited