Lossing pressure in system Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[mcveighpd]

I have a central heating system that losses pressure, I have a header tank in the loft which feeds into the system and every so often, 3 weeks or so, I have to pressurize the system. Can anyone tell me why? or do I have a problem somewhere?

[swidders]

can we have a bit more details about your system please?

do you mean header tank (quite big) or do you mean expansion tank (small - about a foot cube)

how do you "repressurise" it - at the boiler or are you talking about bleeding the radiators?

what sort of system do you have - combi or conventional (with hot water cylinder somewhere)

[DEEARR2]

What type/make of boiler do you have?.

[plumberathome]

[quote="mcveighpd"]I have a central heating system that losses pressure, I have a header tank in the loft which feeds into the system and every so often, 3 weeks or so, I have to pressurize the system. Can anyone tell me why? or do I have a problem somewhere?[/quote] You are contradicting in your question if your system is pressurised you should not have a header tank unless it has an automatic top up sytem fitted with a pump to force the feed water into the heating circuit,instead of a filling loop which is fed of the cold water main. That however does not change the fact that your heating system is losing pressure if it is a combi boiler then check outside to see if the safety run off pipe is discharging water if it is you could be looking at a new pressure vessel for the boiler as the diaphram could have gone ,this vessel takes up expansion in the system as it heats up . Check all the radiator valves for weeping from the spindle or gland under the valve covers best to check when system is cold as everything contracts then and if its going to leak it will.Also check under the floor downstairs if its not a solid floor and if you have pipes under there .If you have a leak under the boards upstairs you should by now have noticed a damp patch on one of your downstairs cielings. Have you had carpets fitted recently? You may have a nailed pipe this can be awkward to find as the leak will be small most times as the nail part seals the problem it has made to sum up you have a leak of some sort it is a matter of finding it unfortunately STEVE

[mcveighpd]

Thanks Steve, will endeavour to look for the leak. The system we have is a condensor boiler which is feed from the tank in the attic. To pressureize the system I have to go into the attic open a tap go to the boiler and open a valve, once it has reached say 1.5 bar, close the valve go back to the attic and close the tap, if I leave the tap open we end up with water running down the wall where the boiler is. I have sealed 2 valves and have looked at the others, but no sign of a leak, but will keep on looking. The sytem is only about 18mths old and was installed by a plumber, would it be a wiser idea to replace all the old pipework? Paul