Ruud
Expansion Control / Over‑Pressurization
Boiler pressure rises excessively during heating and relief valve discharges water
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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
Failed expansion tank (waterlogged), overfilled system, faulty pressure reducing valve, closed expansion tank isolation valve
How to Fix / Troubleshooting
Safety first: Turn off power and allow the system to cool. Hot water discharge from the relief valve can cause burns.
- Check system pressure cold: When the system is cool, note the pressure. If it is already high, the system may be overfilled.
- Inspect expansion tank: Tap the tank—if it sounds solid and heavy, it may be waterlogged. Check the air charge with a tire gauge at the Schrader valve (if diaphragm type).
- Restore air charge or replace: With system pressure at zero and isolated, recharge the tank to the correct pre‑charge (often 12 psi) or replace the tank if the bladder is ruptured.
- Verify fill valve operation: Ensure the pressure reducing valve is not overfeeding the system. Adjust or replace if necessary.
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Repair Difficulty
Medium
3/5
Required Part
Diaphragm Expansion Tank
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