Baxi combi 105HE wont keep pressure?

The internal workings are connected by rubber O rings. They go hard & leak, mine leaked at heat exchanger, on a standard domestic system if you put pressure up to 2 bar at least half a pint will leak to get to zero. With the cover off the boiler you should find it. I also had a pipe leak upstairs and could not find it till the ceiling fell in.

muj
October 2008

check the pressure relief valve (prv) is not passing, hence water pressure lost from the system. prv is connected from boiler to pipe work that should discharge externally. try putting a plastic bag on this pipe and see if it collects any water.

dave pdc
April 2008

If there are no external leaks - in pipework etc, then the leak has to be internal within the boiler, unfortunately. They can be pressure tested if you can find a good heating engineer.

John
April 2008