potterton puma 80e - low system pressure

[felts]

when the heating is not used there is no problem, after the heatings been on the pressure drops and needs to be topped up every couple of days or so.
theres no leaks on any rads and the prv is fine as theres no water coming out of the outside pipe.
any ideas ?

 

[MANDATE]

The pressure will increase by about 1 bar as the heating is used and the water expands and it will drop again as it cools. If you're saying the pressure when cold drops on a daily basis, then there's only one explanation. There must be leak somewhere.

 

[felts]

the pressure only falls after the heating has been used.if the heating isnt used the pressure stays fine.

 

[pannierstan]

the pressure only falls after the heating has been used.if the heating isnt used the pressure stays fine.

The PRV will probably be leaking, but the reason is that the expansion vessel is flat.
You need to fasten a bag on the PRV to defiantly prove it!

 

[edthedog]

The expansion vessel has a car type valve on it. Is it possible to re-inflate the vessel? What pressure should be in it when cold?

Any info would be welcome