Laundry room with a tank-type water heater beside the washer
Generic photo: Alex Tyson · Pexels License

Thermal expansion tank install

An expansion tank absorbs the water that expands as the heater warms it. Set the tank air pre-charge to match the home static water pressure (or the PRV setting) before installing, then mount it on the cold supply to the heater and support its weight.

Cross-checked ~60 min moderateBrands: All

Before you start

  • Turn off the water heater (breaker) and the cold supply before cutting in.
  • Do not exceed the tank's maximum pre-charge or rated pressure.

Diagnostic steps

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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