Boiler losing pressure very fast

[Alepo1]

Have a Vaillant Ecomax 600 boiler only 2 yrs old. We lose pressure down from 2 bars to 0 in less than 3 hrs. 2 engineers have checked the boiler and say it is OK, it must be a leak somewhere. We have no visible sign of leak anywhere. Can somebody suggest what can the problem be? It is hard without hot water for a long time!

Thanks.

 

[gas4you]

Do you have any pipes in or under floors? If so could be one of these.

Pressurise boiler to 2.5 bar. close off ch isolation valves and leave for at least 1/2 hr. if no pressure drop then leak is in pipe work and not boiler. (with thanks to Paul Barker )