Is boiler broken or suffering in cold weather

dander

Since the beginning of this week (ie when it got really cold) my boiler (vaillant condensing combi) has been losing pressure very fast. I'm topping it up at least once a day to keep the heat on. I can't find a leak anywhere. Popped outside to look at the condensate pipe and there's clearly loads of water coming out there - big old iceberg on the wall of the house underneath it. 
Does anyone know if my problem is more likely a boiler fault that has just coincidentally showed up this week, and I need to call a repairman. Or is there something about the cold weather that could be causing the boiler to spit out water? I'm guessing repairmen are not very available right now!

grumbler

dander said:

Popped outside to look at the condensate pipe and there's clearly loads of water coming out there - big old iceberg on the wall of the house underneath it.

You have to check another pipe - pressure relief discharge. The only ways water can escape from the system are leaks and pressure relief valve.

FreeBear

At a guess, I'd suspect the expansion vessel has sprung a leak internally. Unfortunately, to replace this on many boilers will require a Gas Safe engineer. You should be able to find one locally, but you may well have to wait a few days as they are very busy (and charging extra for emergency call outs).

If the boiler is still under warranty, it would be worth giving Vaillant a call and see if they can sort out a repair quickly.

dander

grumbler said:

dander said:

Popped outside to look at the condensate pipe and there's clearly loads of water coming out there - big old iceberg on the wall of the house underneath it.

You have to check another pipe - pressure relief discharge. The only ways water can escape from the system are leaks and pressure relief valve.

ah, yes, it's the pressure relief pipe with the iceberg underneath.

dander

FreeBear said:

At a guess, I'd suspect the expansion vessel has sprung a leak internally. Unfortunately, to replace this on many boilers will require a Gas Safe engineer. You should be able to find one locally, but you may well have to wait a few days as they are very busy (and charging extra for emergency call outs).

If the boiler is still under warranty, it would be worth giving Vaillant a call and see if they can sort out a repair quickly.

10 years old, so no warranty. I'll get someone booked in now I know it won't magically mend itself when the weather warms up. Boiler still works as long as I just keep on topping it up so at least I won't go cold :-)

grumbler

dander said:

grumbler said:

dander said:

Popped outside to look at the condensate pipe and there's clearly loads of water coming out there - big old iceberg on the wall of the house underneath it.

You have to check another pipe - pressure relief discharge. The only ways water can escape from the system are leaks and pressure relief valve.

ah, yes, it's the pressure relief pipe with the iceberg underneath.

In this case FreeBear's diagnosis is correct - expansion vessel. However, it possibly just needs recharging, not replacing.

macman

But it could also be a faulty or sticking PRV? 

Ectophile

macman said:

But it could also be a faulty or sticking PRV? 

Quite possibly both.  Expansion vessel fails.  System over-pressurises and water is expelled through the PRV.  But the water is full of muck from the heating system, which lodges in the valve, so it doesn't close again properly.