Combi boiler experts

DarrenM343 · 2 Nov 2015 at 22:36

Any heating experts here? I'm having a few issues with a boiler. One issue I know of is that it needs a secondary expansion vessel fitted as the pressure goes higher than it should. The second issue which has only recently started is that the heating system is now losing pressure even when the heating is not being used. One reason for this could have course be a leak from the pipes somewhere, possibly caused by the high pressure issue. It wasn't so bad but is now dropping from 1bar to nearly 0 in 24 hours.

While trying to rule other things out, I've found that the white plastic waste pipe from the boiler has a leak. I haven't used the boiler now since this morning (hot water) but at 22:31pm I'm finding the occasional drip still coming from the leaky elbow joint. So, is it possible for an issue to exist that could cause leakage from the heating system into this waste system? The boiler is a Worcester 30 Si Compact. It could be that this pipe is angled so there's water inside does not drain away and it's that, that is leaking but wondering if there's a constant trickle going through it from another source (heating water loop) when it shouldn't be?

In case I have leaky pipes, has anyone tried a specialist companies in finding underfloor leaks using modern tech? Ie, heat sensing devices etc?

Hedge · 2 Nov 2015 at 23:10

The white pipe is a condensate. It's not pressurised and had no impact on system pressure.

Check all your radiator valves and any accessible pipework yourself before getting anyone in.

Is it possible to pump up your expansion vessel with a hand pump?

Hedge · 2 Nov 2015 at 23:12

Oh and if water comes out of the valve when you go to pump the vessel, then the diaphragm is split and you need a new vessel. This would explain your pressure issues.

The valve should be like a bike tyre one.

FlyingFish · 3 Nov 2015 at 07:12

Unlike mentioned above, the condensate pipe can be related to system pressure. If your white pipe is the condensate pipe, and it's trickling water out while the boiler hasn't been operated for a while then it could well be a split main heat exchanger that is leaking the heating water down the condensate drain. Obviously you need to make sure the prv isn't dripping, and that there isn't a leak anywhere else on the system.

If it turns out to be the main heart exchanger then the most cost effective repair is to pay Worcester a one off fee to fix it. It's cheaper than buying the parts required let alone paying someone to do it.

The only downside is that Worcester might be too busy to do the job. Currently in our area Worcester have suspended paid work as they are too busy coping with warranty call outs.

Mick

DarrenM343 · 3 Nov 2015 at 10:02

Cheers for info all. I've checked all visible connections/pipe work and can see no evidence of leaks. As it's a new-ish build all the pipework is hidden in the walls. I can't see any wet patches of plaster or any damp patches in the ceiling which if it is a leak hopefully narrows it down to the ground floor only. if needs be i'll find out who installed the pipework and get them back - at least they may remember how the pipework was laid and where any underfloor connections might be so might be able to avoid lifting too many floorboards.

As the white condensate pipe is dripping I managed to get a glass to catch some of the drips overnight. Without using the boiler since yesterday morning, the glass still managed to catch about a mouthful of water overnight. This could be just water sitting in the pipe I suppose (it's a horizontal one) but as someone mentioned could be a sign that the heat exchanger has a crack. I have enough information hopefully for my gas guy to diagnose any further boiler related issues before we start lookinig for underfloor leaks. I'm sure he'll check the internal expanion vessel.
I bled all radiators last night about 9;30pm, but heating pressure to just over 1 and by the morning was just sitting above the red area, without using any heating or hot water, and as mentioned managed to catch some of the water dripping from the white boiler waste pipe.

The_One · 3 Nov 2015 at 12:49

Pressurise boiler to 1 - 1.5bar

Islolate flow and return CH valves and leave overnight

If pressure has dropped in morning its your main heat exchanger.

If it hasn't then your leak is on the system

DarrenM343 · 5 Nov 2015 at 21:17

Gas guy isolated boiler for a few hours(5) and seems fine - pressure didnt drop.
He has found a blocked expansion vessel - so it was not able to do its job. It's a new build and my gas guy has found plaster blocking it. WIth it now cleared and even though the expansion vessel is not the right size for my property(bit small for no of rads), the pressure is now no longer rising too high and also relief valve not being activated. It was also losing pressure when off(overnight) and I'm hoping what he has done has fixed this too but I doubt it. He also reseated the relief valve in case that was generally leaking after it had been doing it's job. I now have a nervous wait overnight to see what the situation is in the morning. Currently using the heating too to check pressure stays under 2 so won't know until I turn it off overnight and it cools down whether we have fixed the pressure dropping when it's not being users. Fingers crossed, I do not want to be pulling the house apart looking for a leak.

On that note, any know if leak detection experts are worth trying? They use sensing equipment to sense possible leaks.

dholdi · 5 Nov 2015 at 21:38

DarrenM343 said:
On that note, any know if leak detection experts are worth trying? They use sensing equipment to sense possible leaks.

We have used them, but for big systems in secondary schools etc where you have 100's of metres of pipework in underground ducts.
In a house it would be easier and cheaper to get some floor boards up and have a nosy around.