Brain-teaser - another untraceable leak problem

[domg]

Hi all

I am at my wits end and am seeking some practical advice on where to turn next. I live in a converted barn – most of it is open ceiling, with 90% of the central heating pipes running under the celotex that insulates the roof and above the block work that the dry lining is stuck to.

Just before the cold snap in December, the boiler (Ferroli eConcept) conked out with the low pressure warning. The pressure was <0.5bar so I topped it up to about 1.2. Over Christmas I had to top it up during the very cold weather every 3 days or so. Then it practically stopped as the weather warmed up – I topped it up 2 weeks later and it’s continued like that ever since.

There is definitely a relationship between the outside temperature and the rate of the pressure dropping (i.e. the colder the quicker).

However, since Thurs I have had to top it up on Friday and then again on Saturday and the pressure looks like it’s dropping again today.

I must have put about 10 fills of about 20 seconds each in from the top up pipe that feeds the pressure relief tank. Since that’s fed from the mains I’m assuming that’s a lot of water! I cannot find a leak/damp patch anywhere (floors, walls, rads). I have also checked the emergency pressure overflow pipe coming off the pressure relief tank and it does not seem to be dripping. Could it be the pressure relief vessel, with that much water?

I thought the pipe may be cracked in the burner of the boiler but the condensate pipe doesn’t seem to be dripping when the boiler is off. If it was a problem inside the boiler, could the water from the leak be being evaporated and leaving the house as increased steam?

I’ve already had two inspections from heating engineers who have left just shrugging their shoulders. They said I should just wait and watch.

I’m hoping you can suggest where to turn next – it’s driving me mad and my wife is about to chuck me out the house! I'm a complete novice and the forum has already helped me even thinking about the above, but I've run out of ideas.

Many thanks for any suggestions

 

[mickyg]

maybe the heat exchanger is leaking? it is a Ferrolli after all
You need to turn the system off and isolate the boiler flow and returns for a period of time and see if the pressure drops, if it does then your boiler is at fault, and likely the heat exchanger, if not then your system is the problem in which case maybe get some expert leak detectors in like polygon .

 

[domg]

Thanks for that - my hunch is that it's the boiler. We've had loads of problems with it since moving in 3yr ago. It's now 10yr old.

The Ferroli engineer said any heat exchanger leak would come out of the condensate pipe. There's nothing there - but if it could be evaporated in the flue when the boiler's working maybe that's where it's going? I'll put a bucket under the flue and see what it collects.

Thanks for the name Polygon - I'll give them a call.

 

[bengasman]

I take it that the engineers checked the expansion vessel and prv, correct?

 

[domg]

Thanks for the note. We seem to have 2 vessels - one on the floor (with pressure gauge) and one suspended off the pipework near the hotwater tank. The engineers had a glance at them both but since there was no sign of water coming out of the over-pressure release pipe outside I think they just ruled that out. Sounds like I need to get someone in for a good few hours to isolate various parts of the system and see if they can at least rule a few things out.

One thing's for sure - it's suddenly got worse. I'm going to have to re-fill again today for the third day running but no sign of any water/damp anywhere!

Thanks again

 

[Nige F]

Hi all

I am at my wits end and am seeking some practical advice on where to turn next. I live in a converted barn – most of it is open ceiling, with 90% of the central heating pipes running under the celotex that insulates the roof and above the block work that the dry lining is stuck to.

Many thanks for any suggestions

strange place to run the pipes - but could it be running down the celotex and then against the blocks behind the dry lining - if they are Celcon blocks - you can throw gallons of water @ them and it would suck straight into them - in fact you had to when they used to be rendered then set with sirapite plaster . Be careful who you get in - it aint gonna be cheap finding a leak with hi-tech equiptment . I`d try and find a fixed price /no result no fee company . If there is such a thing

 

[bengasman]

Just in case, tie a sandwich bag tightly with a rubber band to the prv outlet, and check daily to see that it is still empty.

 

[gazdaz36]

The only other way I have come across pressure drop with no signs of a leak is when the coil is pinholed on a vented cylinder. The water in the heating system will be lost into the cylinder then comes out of your hot tap when you turn it on.

 

[domg]

Nige - thanks you're right there is a risk of that although the plasterboard is dot and dabbed onto thermalite blocks and so with that much water I was guessing I'd have spotted something by now.

Gazdaz - how on earth did you diagnose the pin holes?? I had considered loss into the hot water tank but it's a high pressure one and the heating engineer's position was that a leak wouldn't force its way into the hot water tank.

The fact that the loss is slow and then fast and then slow again depending on how cold the weather is that's doing my head in.

I'll call someone in tomorrow and give him all your feedback before calling the leak finders given Nige's comment about cost!!

 

[Agile]

Usually leaking water will give a thermal difference on floors/walls.

Using an IR thermometer MIGHT give a clue if the floor/walls are scanned slowly.

Ideally a thermal camera would be ideal but there are only a very few makes and they are very highly priced when they are so cheap to make.

Tony

 

[domg]

Thanks Agile

Is it normal for the flue to be dripping every few seconds when boiler in use? I think that may be the problem which I guess is something to do with the heat exchanger / condensate? I'll collect half a bucket full in a few hours + whatever is going down the condensate pipe.

Hopefully that and not digging up floors!

 

[boilerdoktor]

Thanks Agile

Is it normal for the flue to be dripping every few seconds when boiler in use? I think that may be the problem which I guess is something to do with the heat exchanger / condensate? I'll collect half a bucket full in a few hours + whatever is going down the condensate pipe.

Hopefully that and not digging up floors!

if water drips from the flue then the angle is wrong it should rise slowly up off the boiler (3degrees ish) so the water condensates back through the boiler! This wont affect pressure loss!

Isolate the boiler at the flow / return isolation valves after filling it to 2.8 bar. leave for an hr or two. if you return and the gauge is the same open the iso valves. if the pressure drops its on your system. if it has dropped before you open the valves its on the boiler.

remove the cap on the scraeder valve on your expansion vessels...have you got air in them?? if all the above are checked and positive i would be looking at the cylinder!

 

[domg]

Thanks boilerdoktor

That's a great suggestion - there is air coming out of the PRV and so I'd be surprised if it's that. I still think it's the boiler but the Ferroli engineer said there was no way any leak in the heat exchanger could be boiled off in the flue and released as condensation.

How on earth do you check the cylinder? He also said that couldn't happen because the hot water cylinder is at mains pressure and so any leak would cause water to go into the pipework and not the other way.

Still no sign of any damp!