Looking for a leak

John Rumm · 2019-03-09T18:25:08+00:00

So far all the normal tricks don't seem to be doing it!Short version:There is a leak somewhere in my central heating system - its losing pressure regularly, and needs topping up with at least a couple of litres a day.Longer version:The pipework is of questionable vintage, but I am guessing 30+ years old. Almost exclusively copper apart from about 3m of speedfit for one particularly awkward pipe run. Largish S Plan+ system - unvented cylinder and about 21 rads (split into separate upstairs and downstairs zones).The system was pretty good - only needing a small top up at most once or twice a year. However over the last year its got worse. It got to the point where it needed a top up every other week or so. So I carefully checked around any areas where there have been changes in recent times.I found one radiator tail in the downstairs loo where I had needed to do a "live" pipework change and had used a cuprofit fitting that was knocking about in the plumbing kit. That had a very slight indication of a weep from around the base of the fitting. So I chopped it out and re-did it properly. After that, no improvement or the rate of loss seemed to get even worse! Even though there is definitely no evidence of a leak in that location now.So I checked the PRV drain pipe on the system boiler. That's not letting by. Checked the drain point tap which is outside - again its dry.Seems unlikely its the coil in the indirect cylinder since it is an unvented cylinder, and the water pressure inside it is higher than that of the CH primary - so if that leaked the CH would fill up!So I had a careful look about. No indications of staining on the ceilings, and it seems unlily one could lose that much water by evaporation from the leak point. so I thought ground floor would be more likely - there is loads of space in the under floor void where you could lose water without it showing up anywhere.However over the last few weeks I managed to get eyes on pretty much all the GF pipework...

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John Rumm 7 years ago

I think I have found mine as well....

Having finally got access to all the ground floor pipework (lifting floors etc), I found - erm nothing!

So today while the heating was on setback I decided to make some checks on the boiler itself. Lifted its pressure to about 1.5 bar, and then turned its power off. I thought that I would also check the condensate drain. Interestingly - normally its spotlessly clean and full of clear water. This time it looked decidedly orange and slightly scummy. So I emptied and cleaned it and put it back, then left it alone for a couple of hours. Had a look again and its now 3/4 full of water. Emptied again, left another hour or so, and verified that the system pressure had fallen a little. (I replaced a rad vent plug with a larger pressure gauge to be able to more clearly see the difference without the aid of the boilers electronic gauge).

So the good news is at least the plumbing is ok, and I have not got to fix something in some awkward difficult to get at place. The less good news is it looks like the primary HEX mush have a small internal leak.

Quite how/why that happened on a 7 year old boiler on a well cleaned system that was always treated with inhibitor I am not sure. I suppose until I look in the combustion chamber its hard to say what is going on.

Replacement HEX seem to range from £120 for a reconditioned one, and new ones ranging from £220 - £450 depending on where you get it.

Now I know its not leaking water into the house I may just slap in some more inhibitor and leave it until the warmer months!

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harry 7 years ago

You can get a chemical additive leak sealer. (Similar to "Radweld") How effective it would be in the HEX, I don't know.

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Tim Lamb 7 years ago

In message snipped-for-privacy@brightview.co.uk>, Jim K.. snipped-for-privacy@gmail.com writes

Plumbing fibre washers seem closely related to gold dust in terms of availability.

When this cropped up before, I bought a pack from e-bay. Sadly the larger sizes are too narrow to function properly.

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Tim Lamb 7 years ago

You were right. The agricultural solution failed once the hot water reached the manifold.

I have shortened the coupler by turning off the spanner flats. Fortunately I have a set of *Mole* grips with curved jaws which were a good fit on the remaining body. More mait and it was running OK last night.

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RJH 7 years ago

On 16/03/2019 09:28, Tim Lamb wrote: snip

Not cheap, but sets from Screwfix:

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Brian Reay 7 years ago

We have a normal, pumped, system, which after a few years developed a leak while we were on holiday. Middle daughter was house sitting and noticed a puddle under the boiler in the garage, turned off the heating, stuck a dish under it, and rang us- interrupting a very pleasant sunset and bottle of wine- for further instructions. Fortunately, being summer, she only needed hot water and could manage with the immersion heater until we returned.

We have service contract with a local firm (which has always been excellent) and I happened to be there just as he removed the cover from the heater exchanger- to see him get drenched in water. There was a leak in the heat exchanger. Most of the innards of the boiler were replaced FOC within a couple of days. It seems, while not common, it is far from unknown. He reckoned it was due to Aluminium heater exchangers and was virtually never a problem in the days of cast iron ones. So much for progress.

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tabbypurr 7 years ago

The one used in CH is water glass. It sets hard when exposed to high temp. IMLE (sample of 1) it sort of worked, but not fully, and that was with a vented system with a few feet head above the boiler. It does result in hard but easily broken off crud getting into the burner area. I presume minimising pressure would help, which might be helped by putting a bit of air into each rad.

NT

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John Rumm 7 years ago

I did try some on this, and it appeared to work for about 5 days. It might be that the stresses are too high on a HX, or might be I did not have adequate concentration for the quantity of primary water in the system.

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Roger Hayter 7 years ago

Yes, tap connectors are horrible things. I was forced to use them behind a siliconed-in tile and have had nothing but trouble. Usually due to rigid pipework not lining up 100% so the washer is unevenly compressed. Gross over-tightening seems the only solution. If there is room, a tapered, sealed threaded connection with a nearby compression joint for dismantling is more reliable. Or even a proper union connector to be posh!

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tabbypurr 7 years ago

I expect you have a pressurised primary. The last boiler ran on waterglass with a split HX.

NT

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Tim Lamb 7 years ago

In message snipped-for-privacy@brightview.co.uk>, Jim K.. snipped-for-privacy@gmail.com writes

It is the sort of component you need to see before purchase:-(

I tried several plumbing outlets without success when I needed to fit a parallel thread 22mm tap connector to a wall fitting.

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Tim Lamb 7 years ago

In message snipped-for-privacy@brightview.co.uk>, Jim K.. snipped-for-privacy@gmail.com writes

Yes:-) The on-line pack I bought has a 22mm washer but it is only about 2mm wide. Trapped in a socket, it would be fine but where there is room to spread, unreliable.

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John Rumm 7 years ago

Indeed, its a sealed system (although peak pressure does not exceed 1.7 bar normally)

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Jim K.. 5 years ago

Bit of folded bike inner tube + jubilee clip = sorted for years...

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Jim K.. 5 years ago

Is that from Viz? :-)

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Jim K.. 5 years ago

I think I'd have started with that!

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Jim K.. 5 years ago

Toolsatan similar for £10 odd or eBay....

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Jim K.. 5 years ago

A fibre washer?

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