Pennco
Overpressure / Expansion Tank Failure
Pressure relief valve discharges water periodically
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Safety Warning
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.
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Possible Causes
Waterlogged expansion tank, Overfilled system, Faulty pressure reducing (fill) valve, High limit aquastat set too high
How to Fix / Troubleshooting
Safety first: Hot discharge from relief valve can scald. Use caution.
- Check pressure: Observe the boiler pressure gauge when cold and hot. If pressure rises above 30 psi, the relief valve will open.
- Inspect expansion tank: For diaphragm tanks, check air charge with a tire gauge (with system pressure at zero). Recharge or replace if the bladder has failed.
- Verify fill valve: Ensure the automatic fill valve is not over-pressurizing the system. Adjust or replace if necessary.
- Do not cap relief valve: Never plug or cap the relief valve outlet. Replace the valve if it drips even at normal pressure.
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Repair Difficulty
Hard
4/5
Required Part
Expansion Tank
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