Loss of pressure in the CH boiler system

[KJB]

Hi, i have a fully pumped pressurised (sealed) CH and HW system. The accumulator pressure drops regularly to zero. I cannot find a leak or any other evidence of a problem, what do we think it can be please?
Other info if it helps.
Ideal classic FF260 boiler - non condensing

 

[gblades]

Check the PRV (pressure relief valve) which normally vents to outside. make sure the pipe is dry.
If you pressurise the system and then turn it on what is the pressure when the rads are all up to temperature?

If the PRV is dry then its normally a leak somewhere on the pipework. Check the connections by all the radiators.

 

[Steady]

Not always going to be a leak.This is also a symptom of a faulty pressure vessel. Do a search on here. It may be possible to recharge it-unless the diaphragm is gone.

 

[gblades]

Thats only a cause for the pressure to get too high and then leak out of the PRV.

If pressure in the system is dropping then there has to be a leak somewhere either intentional such as the PRV or in the pipework or from another component.

 

[Steady]

Thats only a cause for the pressure to get too high and then leak out of the PRV.

Sorry, but that's not correct. Faulty pressure vessel causes both pressure loss and pressure increase. many threads on here saying the same.

Eg here:

http://www.diynot.com/forums/viewtopic.php?p=249578#249578

or here:

http://www.diynot.com/forums/viewtopic.php?p=82922#82922

or here :

http://www.diynot.com/forums/viewtopic.php?p=505038#505038

or here:

http://www.diynot.com/forums/viewtopic.php?p=1179345#1179345