worcester bosch 35cdi pressure dropping

[FlowGas]

Hi everyone, just had a call from a family member (knowing im gas safe now) asking me to come around and check out their boiler. They said everything seems to be running fine dhw and central heating, there's also a megaflow hooked up. but the pressure seems to drop, any ideas as to what it could be, I'm reading the manual now and searching the net for a potential diagnosis of the problem.
If any of you have any experience or knowledge as to the possible issues that may be causing the pressure loss , please do share.

 

[mountainman]

What pressure seems to drop, system, mains, hot, cold, gas?

 

[ManchesterGas]

I'm guessing pressure drop on CH gauge?. There is a leak from the sealed system, could be anywhere.

 

[mountainman]

If it's system then check the PRV for discharge.

Sooo many things can cause system pressure to drop that the possible answers could make this a record breaking thread

 

[Blumper]

Could you really get to be GS registered without having the first clue as to what could cause a combi system to lose pressure ?

 

[Hybrid]

Could you really get to be GS registered without having the first clue as to what could cause a combi system to lose pressure ?

Apparently.

 

[Mike Jackson]

Being fairly old now my money is on the EV.

 

[FlowGas]

Hi guys, I was aware that it may have possibly been a leak in the system, like I've said previously I am quite inexperience and therefore asked you guys for possible common faults with that particular boiler.
(Mike jackson) you were absolutely right it was the EV, advice and guidance is much appreciated.

 

[wazzer]

Stick a balloon on it you cant always spot a drip in the rain.

 

[stratplus]

Out of interest how do you know it was the expansion vessel? and how did you rectify it?