No pressure on combi-boiler

[boydycx]

Hi Folks
The pressure on the combi constantly drops to near zero and if i fill her up it only lasts a few days and is back to zero.
Even though there is no pressure i am still receiving hot water and the radiators are heating up.
All advice accepted.
Thanks in advance.

 

[Gees]

Find the leak............

 

[ChrisR]

Is the Pressure Relief pipe producing any water? (That's the one which normally goes straight through the wall.) If so your pressure vessel needs re-pressurising.
To do that you have to release all the pressure from the system and pump up the PV with a foot pump or similar, to about 1 bar. Not trivial if you don't know where things are.

Often PR valves do just leak, too.

 

[boydycx]

Thanks guys.
I have just pumped it up to 1 bar and it has hissed its way back to zero. Does that mean i need to change the valve or could there still be a leak? If i leave the pump attached it stays consistant at 1 bar.

Steve.

 

[ChrisR]

Wot h issed If it was the schraeder valve its just like a tyre valve - unscrew, clean and replace. If you can get at it it'll be a b**o*y miracle though. You could try poking the centre pin several times....

Sometimes the pressure vessel is simply too difficult to change, you have to dismantle the combi completely while it's off the wall in some cases! If that's the case you forget about it (blanking if necessary - not nec unless the diaphragm has perforated) and fix another one to an accessible pipe somewhere. Supposed to be as near as possible on the return side. Not a major drama.

 

[boydycx]

Thanks Chris, yes it was the tyre valve and will try to clean it.
Thanks mate you must have saved me a small fortune.
Steve.