Plumbing Problems in the UK? Ask a Plumber Now.
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Are you currently experiencing water dripping or running from the relief valve?
Boiler over pressure can be caused by a couple of issues. Firstly, the makeup water pressure reducer valve has failed or has some debris caught in the the valve keeping it from closing and water slowly enters the system. Second, if you have multi turn or gate type valves the washers and seals can wear out and allow water to enter the system. The other problem could be the expansion tank has ruptured and the heated water has no relief for the pressure buildup when the water is heated. Make sure that all valves that supply water to the system are closed and observe to see if pressure continues to build. Let me know what you find.