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Is there a thermal expansion tank installed on the domestic supply piping
and is it properly sized? (Non-Warranty)
- A thermal expansion tank is required if the domestic supply piping includes a backflow
preventer or pressure reducing valve.
- Ensure the potable water expansion tank is properly sized according to the water heater
volume and supply pressure.
- During long periods when there are no draws from the tank (i.e. overnight), the T&P
relief valve may lift or weep due to thermal expansion, but may function properly during
normal periods of tank draws.
Is the expansion tank defective, water logged or improperly charged?
(Non-Warranty)
- Check for failed gaskets or bladders, or a faulty Schraeder valve.
- Use a tire gauge to check the charged pressure of the tank.
Is the temperature/pressure relief valve functioning properly?
- Dirt and water deposits can accumulate under the valve seat.
Check the domestic supply pressure entering the water heater.
(Non-Warranty)
- If the pressure is over 70 psi, it is recommended to install a pressure reducing valve. This
will prevent any pressure spikes or increases in pressure due to thermal expansion which
may cause the T&P valve to lift or weep.
Check the domestic system for possible sources of water hammering or
pressure spikes.
- Some appliances, such as clothes washers and dishwashers, utilize fast acting valves which
may cause water hammering or pressure spikes through the domestic water system.
Action Item:
- Install water hammer arrestors as required per the manufacturer’s instructions, or install
flexible connectors to isolate the tank from the domestic system.
Check the operating temperature of the boiler.
- If the boiler operating temperature is excessive, greater than 200ºF, stacking can occur in
the inner tank raising the domestic water temperature close to the boiler operating
temperature.
Action Item:
- Reduce the boiler operating temperature to 180ºF.
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