How to Fix / Troubleshooting

Safety: Allow system to cool before relieving pressure. Use caution when opening any valves.

Steps:

1. Check cold pressure: When the system is cool, pressure should be around 12–15 psi. If much higher, reduce pressure by draining water from a boiler drain while monitoring the gauge.
2. Inspect expansion tank: For diaphragm tanks, press the Schrader valve briefly. If water comes out, the tank has failed and must be replaced.
3. Verify tank charge: With system pressure at zero and tank isolated, check air charge with a tire gauge; it should match system design pressure (often 12 psi). Repressurize with air if low.
4. Check fill valve: Ensure the automatic fill valve is not overfeeding. Replace if it does not regulate properly.

Professional help: If pressure problems persist, have a technician evaluate the expansion tank sizing and piping.

Boiler pressure rises excessively when heating, relief valve opens frequently

Possible Causes