American Water Heaters Excessive Pressure or Thermal Expansion

Water heater relief valve or nearby piping makes a hissing or whistling sound.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

No expansion tank in closed system, Failed pressure-reducing valve, High municipal water pressure, T&P valve beginning to weep

Safety: Do not cap or restrict the T&P discharge. High pressure can be dangerous.

1. Measure pressure: Attach a pressure gauge to a nearby faucet and monitor static and dynamic pressure.
2. Install or service expansion tank: In closed systems, ensure a properly sized expansion tank is installed and precharged to match system pressure.
3. Service PRV: If incoming pressure is too high, adjust or replace the pressure-reducing valve.
4. Replace T&P valve if leaking: If the valve is hissing and dripping, replace it with a properly rated valve.

Medium 3/5

Thermal Expansion Tank and T&P Valve

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