Leaking combi boiler

18 Feb 2013
Reaction score
West Midlands
United Kingdom
Pressure gauge when the boiler is off is 1.5 bar.
After turning on CHS, pressure steadily rises to 3.5 bar over a period of about 10 minutes.
Then it starts discharging water from the bottom of the boiler onto the floor.
No leak occurs until pressure hits 3.5 bar.

I can't find the stated 'pressure release valve', but the leak seems to be occurring from behind the heat exchanger part - it's all dry above and below it.

Boiler is an Ideal 24.

Any ideas?
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when was it last serviced? has the expansion vessel ever been pumped up?

when you go outside, can you see a copper pipe poked through the wall behind the boiler, and curved round to point at the wall? is it wet?

post some photos
It was last serviced last year, and last fixed about 6 months ago (Now on it's 4th Main PCB and 3rd Gas Valve).

I would imagine the expansion vessel has been pumped up as it was installed about 6 years ago (and broken down about 5 times since then!)

Outside there is a copper pipe poking out, but its not pointing at the wall, its pointing straight out from the wall, no bends in the pipe, its right next to a plastic pipe that goes down and then around the corner of the property and then then ends up in the storm grid.

I've dropped the pressure now to 0.5 bar, and it seems that as soon as the pump kicks in, it bolts upto 1 bar and seems to settle at just over 2 bar after the burners have been on for about 10 minutes, then gradually drops down again. No more leaks so far.
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Scrappydo, time you gave crappy boiler person a miss and get someone real to fix your boiler ;)
The expansion vessel has either failed or has not been repressurised by the scrappy person you have doing your servicing.

The pressure relief valve vent doies not seem to have been connected and that is an offence under the Building Regulations. It could also kill a small child playing near the boiler when its vents boiling water!

The installer should be hung! Why not name him?

Had two different engineers come out and look at the boiler, apparently the heat exchanger has degraded and has at least one hole in it! Less than 6 years old so I'm kinda surprised by this.

Said they need to completely remove the boiler from the wall to replace the heat exchanger, and they have none in stock and it's a 2 man job, so it'll be about 4 weeks before it can be repaired.

Now thinking whether I should stump up the cost of the heat exchanger (£400) or just have it ripped out and another boiler put in its place. I remember last week having a leaflet through the door for Worchester Bosch boilers, are these considered decent quality?
Knowing its an unreliable boiler why don't you have a repair insurance with British Gas?

Surely a fixed price repair from Ideal is the way to go?

I still don't know what boiler model you have! A "24" does not tell me anything!

By the way, I am still not at all convinced that the heat exchanger is failed!

What is failed is the expansion vessel but none of your engineers are repressurising that.

You really do seem to have been calling some scrappy engineers. Do you find them in the pub?

If you lived nearby then I would come free to see just what is wrong. But I would not tell you unless you paid a diagnostic fee.

Sorry, it's an Ideal ISAR HE24.

Thanks for the diagnostic, but 2 separate engineers can't give the same incorrect diagnostic, surely.
if you have to pay £400 for a new hex, then get it ripped out, isar's are one of the biggests piles of crap ever made, not worth spending anything major on it

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