vaillant boiler keeps losing pressure

[francis chinery]

I have a vaillant boiler VC GB 242 EH and when i fill the system back up with pressure after about 6 hours the pressure goes down,it seems that the boiler fires up and just keeps on going and then pressure gauge goes up to max then looses pressure.
I was told by one plummer that the exspansion vessel may need to be re-charged how do you do this?
can anybody help

 

[bobw1956]

unless you know what you are doing, call a heating engineer.
otherwise do a search on the subject, its been a topic many times.

 

[corgiman]

as bob says maybe better to get someone in

it sounds like your plumber (not plummer ) is spot on why didnt he do it for you?

also maybe best to replace the expansion vessel.