A leaking combination boiler overflow pipe can be a sign of a problem with your heating system or boiler. It’s essential to address this issue promptly to prevent further damage and ensure the safe operation of your boiler. Here are some steps you can take to address a leaking combination boiler overflow pipe:

1. Turn off the boiler: First and foremost, switch off your boiler to prevent any additional water from being released through the overflow pipe.

2. Isolate the water supply: Locate the water supply valve to your boiler and shut it off. This will stop the flow of water into the boiler and the heating system.

3. Check the pressure: The most common reason for a boiler’s overflow pipe to leak is high pressure in the system. You can check the pressure gauge on the boiler. If it’s reading too high (typically above 2.5 bar), you may need to reduce the pressure.

4. Bleed radiators: If the pressure is too high, bleeding your radiators can help reduce it. Use a radiator key to release air from the radiators until the pressure gauge returns to a safe level (usually around 1-1.5 bar).

5. Check for blockages: Ensure that the overflow pipe is not blocked or obstructed. Debris, ice, or other obstructions could be causing the leak.

6. Inspect the pressure relief valve: The pressure relief valve may be faulty and need replacement. It’s responsible for releasing excess pressure from the system. If it’s leaking, it may need to be replaced by a qualified technician.

7. Call a professional: If you’re unsure about any of these steps or if the problem persists, it’s best to contact a qualified heating engineer or plumber to assess and repair the issue. Boiler and heating system repairs should be performed by professionals to ensure safety and compliance with local regulations.

Do not attempt to repair the boiler or heating system on your own unless you are a trained and certified professional. Boilers can be dangerous if mishandled, and improper repairs can lead to serious safety risks. Always prioritize your safety and the safety of your home when dealing with heating system issues and find your professional on Tradescope