Boiler Pressure Loss? - Plumbing Forum | Plumbers Forums

mbird59 · 08-03-2008

I have a problem where my boiler keeps losing pressure. I have had a new boiler fitted in the last few months but have/had the problem with both the old and new boilers.

It seems that when I go around and bleed the radiators etc. the problem becomes even worse in so much as when we get up every morning the boiler pressure has dropped to zero. Then over a period of months the problem becomes less acute and we just have to top up the boiler a little every week. I went and bled the radiators again and one particular rad had a LOT of air in it (just as before) which I bled and now we are back with the problem of the boiler pressure dropping to zero.

Is it possible that the radiator that keeps requiring a lot of bleeding could in some way be the problem be causing the pressure problem?

I do not have any water being discharged through the overflow and I have searched high and low but can not find a leak anywhere.

Any help much appreciated.

Michael

**uug197h** · 08-03-2008

you have a leak on the system thats the only way you can be losing pressure

mcmoby69 · 09-03-2008

its your expansion vessel, either needs pumping up or it needs replacing. when you repressurise the system in the morning the system is cold. turn the heating on and the water heats up expands and discharges out the prd.when it gets below 3 bar pressure it stops discharging and carries on running because the hot water is expanded. when the heating goes off the hot water cools(contracts) and looks like you have lost pressure, sometimes it loses enough pressure to stop the boiler firing up on its next set time. if you watch the pressure guage when you fill up you will see it pressurises quickly because the diaphragm in the expansion vessel is either perforated or the vessel needs recharging with air. bike pump required!

10-03-2008

The boiler (Vokera) is brand new and as I had the problem on the old boiler is it still likely to be the pressure vessel?

The combi boiler only heats the water for the showers other than this it has a traditional copper cylinder/emersion. I have searched everywhere for a leak is it possible the leak could in some way be in the cylinder?