Hydronic Water Expansion Tanks

1-Year Limited Tank Warranty*

Hydronic Water Expansion Tanks by American Water Heaters

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Sizing Calculator


American Expansion Tanks for closed space heating systems provide a place for expanding water to go during cycles of thermal expansion, eliminating the risk of damage to the boiler and piping in the system.

  • • For use with space heating boilers in closed systems — not for use with potable water heating systems
  • • Models up to 14.6 gallons feature in-line design for installation directly into system piping
  • • Field-adjustable 12 PSI air charge
  • • Drawn-steel tank
  • • Butyl diaphragm, for permanent separation of air and water, with no waterlogging
  • • Maximum Working Pressure: 100 PSI
  • • Maximum Temperature: 240°F
  • • 1-Year Limited Warranty

Hydronic Water Expansion Tank Sizing Chart by American Water Heaters

Sizing based on the following operating conditions: Cold pressure 12 PSI, Relief set 30 PSI, maximum temperature 240°F. Sizes shown are for fin-tubed baseboard radiation. For systems with converters and/or unit heaters, increase tank one size. For cast-iron radiation, increase tank two sizes.

For larger systems, it will be necessary to calculate the expansion of water within the system. Our engineering department can assist you, if you provide the size of the system in gallons, the pressure, and the maximum operating temperature. If you do not know the system capacity, it can be calculated from the amount and size of pipe used.

Download Spec Sheet

Download Owner's Manual