water is dripping out my boiler overflow....

sallyrsm

and obviously when the heating is on, it's hot water!
It's not so much a drip as a constant trickle...
what could be wrong with it before I call a plumber and get taken for some sort of numpty if they start talking "flux capacitator"... ??

ormus

what make/model boiler do you have and what sort of ch system?

sallyrsm

it's a Vokera, don't know the model, and it's a combi?
you know, you turn the hot tap on and it makes hot water? I've got no hot water tank.

ormus

if its a combi condensing boiler, then liquid condensate is supposed to drip out of the "overflow pipe".

sallyrsm

I don't think it's supposed to drip at this rate... put it this way if I was on a water meter I'd be seriously watching money go down the drain....
I could fill a pint glass of water in less than two minutes, that isn't right is it?

djheath

The pressure relief valve has activated. This usually happens when the pressure in the boiler gets too high - at 3 bar. It can be caused by not having the expansion vessel, ( a big plastic thing at the back of the boiler that is filled with air. This absorbs the natural expansion of the water when it is heated for central heating), at the required pressure. Or it can happen for other reasons - blockages, broken relief valve etc.
Could be the filling loop is still attached, but as you say it happens when hot then less likely.

They dont usually work very well after they have let water through so usually need to be replaced.

What is the pressure reading on the boiler when it is cold and what is it reading when the CH has been on?

If it is emptying as quickly as you say it is, then I doubt there is much water left in your central heating system now.

I wouldn't use the boiler until a plumber has seen it.