Alpha CD50 Condensing Combi Boiler - persistant leakage.

[frankino]

The above boiler was fitted in current property approx. 4 years ago when new - and I have recurring leakage problems regularly.
It either 'dumps' directly under the boiler or/and projects water (with system presssure I assume) approx. 12" to 18" in front of the boiler soaking the carpet.
Just last week I called out plumber under service contract and he fitted new gaskets in bottom manifold? I think, but the pressure has started falling again and tray I have located under boiler has started to fill slowly with water again.
The thing is I have never witnesssed the leakage and I never see any evidence of leakage ie water on pipe threads/ on pipe or drips, although I realize the heat may evaporate this.
Is it possible that there is some sort of blockage and at a certain pressure there is

[Cheesie1]

It sounds like ur boiler is over pressurising then dumping, this is usually caused if the expansion vessel is flat (but it should dump out ur prv (copper pipe outside) if the connection is not tightened could be leaking internally (this would explain the high pressure dump), try running heating and watch pressure gauge, if rises quickly and above 3bar will dump pressure via prv, if this happens re pressurise expansion vessel, also this boiler has had a manufacturers letter sent re the pipe from flue collection to trap (rotting needs replacing) if u get in touch with Alpha they will send u the part free of charge.

[boilerpain]

i dont know If my particular problem is covered by the info already posted.....

When I select water only rater than water & heating, the boiler loses pressure over night (or over a period of a few hours) to the point that the boiler does not operate when hot water is required.

water appears to dump on left hand side as viewed from front (in vacinity of fill connection but not related to...)

Boiler repressurises easily enough and operates as norm

Any thoughts folks???