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Amtrol ST-5 Thermal Expansion Tank

by Amtrol

Amtrol invented the thermal expansion tank to absorb expanded water in closed, hot water systems and protect the water heater. Since the beginning, we’ve kept the pressure on our competitors with features they just can’t match; like our patented Turbulator™, patent pending antimicrobial liner, patented InSight™ service indicator cap and 50 PSIG precharge. When your water heater is on the line, we deliver.


  • Shell: High Strength Steel
  • Diaphragm: Heavy Duty Butyl NSF/ANSI 61
  • Liner: Antimicrobial
  • System Connection: Stainless Steel
  • Water Circulator: Patented Turbulator™
  • Air Valve: Projection Welded
  • Air Valve Cap: Patented InSight™ Indicator Cap
  • Factory Precharge: In-Line Models: 50 PSIG (3.5 bar)


  • Max. Operating Temperature: 200º F (93º C)
  • Max. Working Pressure: 150 PSIG (10.3 bar)
  • Warranty: 7-Year Limited


  • For use in closed, potable hot water systems to control pressure build-up and protect the water heater.
  • Accepts expanded water as system temperature rises and returns hot water to system when demand occurs.