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Comb boiler reading

My combi boiler currently sits at 2.8 bar and rises to 3.0 bar when the heating or hot water is on. Is this normal? There does not seem to be any problems with my hot water or heating . Can someone advise?

If this needs to be reset to 1.5 bar, how can I do this? And can someone advise? I live NW10 way London

2 Answers from MyBuilder Plumbers

Best Answer


It's perfectly normal, when you turn on the system hot water is heating up and in turn expands creating more pressure in the system.
Although 3 bar is on the upper limit for a combi before pressure relief valves come into play, the system could do with being set around 1.5 - 2 bar.


Answered 18th Sep 2012


2.8 bar is too high. When the system is cold the pressure guage should be around 1 bar (dependant on the boiler make and system size). If the pressure guage is reaching 3 bar and there is no water discharging from the pressure relief pipework, then i would suggest you get the system checked by a professional. It may just be a case of bleeding some air out of the rads or letting a small amount of water out of the system in order to drop the the pressure, but the fact that its reaching 3 bar without any apparent pressure loss through the pressure relief valve could be a sign of a problem. If your boiler is due for its annual service now would probably be a good time to book it in, as any competent heating engineer will be able to advise if there is an issue.

Hope this helps.


Answered 18th Sep 2012

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