Vaillant thermocompact leak

System boiler, just under 2 years old.
Suddenly losing pressure rapidly, plumber can't find, so leaky h/e crossed my mind as a possibility. Anyone had one leak?
Warranty? Says I,( haven't visited yet.)
Vaillant say no becasue the boiler (she told them) wasn't serviced at end of year 1. Their callout charge £215.

If it IS the h/e I'll fill in the benchmark service record for a year ago, assuming a service would have made no difference!

Why do you think its anything different from the PRV this time ???

Because the plumber whom I mentioned had a good look at that (It was Peter B) along with rad valves and the aav.

In that case I would still expect it to be the PRV as prime suspect!

You don't trust him then?!

Exp vessel pressure ok, PRV dry. Sealed ch but open vented HW, so I suspect the cyl coil may be perforated.

Not easy to prove. The water n the DCW cistern has certainly been above the fill level, but the expanding DHW would make it do that.

Cistern is a biggie so the few litres coming from the ch would hardly make its level rise much.

It's the 37kW thermocompact, non condensing. All dry inside though a bit of green fur on the h/e in one corner like lots of boilers. Again, seemed dry even when cold.
If its anything like the Turbomax pressure switches, the boiler keeps going down to a tiny pressure. But this one stops. Two victorian floors means the boiler pressure shouldn't go below 0.6 bar or so if the coil IS holed.
2 bar to the .6 or so bar I saw, had taken about a week, so its a middling sort of leak.