closed loop heating loses pressure

[Mikeyp]

I am in the process of having a loft conversion. In order to do away with the header tank I have had a pressure vessel fitted into the system by a qualified plumber.
Everything seems to work fine except that it loses pressure regularly since fitting, and I cannot find any leaks at all anywhere.
What is inside the pressure vessel, apart from water? Is it just a void or is there a spring and diaphragm?

Any suggestions?

 

[stardanny]

How do you know it losing presure? Gauge? What it say on it?

Might be pressure vessel faulty?

Maybe there a leak you hadn't look yet?

 

[Mikeyp]

the pressure guage is supposed to read 1b and I am regularly topping up sometimes within 24hrs.
No sign so far of awater at the overflow pipe/prv. But I've bagged it tonight to see if it fills with water.

 

[bengasman]

any water coming from the prv?

 

[Mikeyp]

Thats why I've bagged to overpressure pipe to see if it catches any water.

 

[stardanny]

If you say pressure vessel and PRV is new, then maybe there a leak somewhere in the house. Check all radiators, radiator valves, pump, motor valves, boilers and all the heating pipework. Maybe you have pipes running under concrete floor or wooden flooring? Pinhole leak can cause pressure to drop.