Combi Boiler Pressure Keeps Dropping

[Robert Knight]

Hi. I have a combi boiler that keeps losing pressure and I have to top it up. I'm having to do this once a day. My local plumber says that it's the "expansion vessel". However, he said that if it was the expansion vessel then the pressure would shoot up when hot water was demanded but would then drop back. This does not happen I.E. the pressure does not shoot up when hot water is demanded it remains about the same as it was. The expansion vessel is inside the boiler and hard to access and he suggests a new boiler. The boiler is about 21 years old. What do people think? Could it be something more simple than the expansion vessel.

Thanks.

 

[ReganAndCarter]

You're in the wrong department - need to be posting this in Plumbing & Central Heating.

Plumbing and Central Heating

Questions, comments and enquiries related to plumbing, central heating and hot water systems.

www.diynot.com

First thing to check is where all the water is going. Poss dripping out of the blow off/temp & pressure relief pipe outside. If can't see it dripping, tie plastic bag over end of it and see if it fills up. If not need to see where else all the water is going. Could be leaking hidden pipework to rads. A clue as to which boiler you have would be another good thing.