Central Heating Losing Water

[Doug99]

My son owns a 7 bedroom house with a Worcester Combi (10 years old) and is having to top up the heating system's water pressure once a week. Despite our efforts we are unable to locate any leaks. All rads are bled as the system is re-charged. The weekly top up implies that the sytem is sufferring from a significant leak, but all radiator/boiler fittings are sound and there are no obvious damp patches. As I type, have just thought of a possible leaking pressure relief valve?

Any other ideas before we start lifting floorboards?

Cheers

 

[Softus]

Usual suggestions:

1. Bag over the PRV pipe.

2. If you have working isolating valves on the CH flow and return, pressurise the system and then turn them off.

This will show which side of the isolating valves the leak is. As long as you can afford to keep the system off for a few hours.

3. Check all rad valve joints very carefully when the system is stone cold - when warm the water from all small leaks will evaporate before you can see it.

 

[gas4you]

Drain down shut heating isolation valves on boiler and air test heating circuit with compressor.

Has boiler been fitted with scale inhibitor? Does pressure increase above 3 bar when heating/hot water on. Could be heat exchanger scaled up. as previous suggetsion plastic bag over PRV discharge pipe. Is hot water constant or does it go cold/cooler the warm again?