Central Heating Leak, Grrrrrrrr!

[Martin King 2Participant @martinking2]

Hi All,

We have been in our house now 20 years and love living here in lovely Dorset.

House was built 1988 by a local, now long defunct, company who were total; t*****s and left us a litany of problems as the second owner, most of which I was able to fix. A lot younger then of course!

One such problem was that one day we noticed a musty smell in our utility room and on lifting the lino floor covering there wwas a damp spot in the concrete floor. After careful excavation and a lot of swearing i got down to the offending copper pipe to be greeted by the finest mist like spray possible.

Cause: the idiots had laid the 15mm copper straight into the wet concrete floor with no hessian or protective covering whatsoever. It was REALLY difficult to find enough room to get some slack and cut out the bad section as it was close to a wall. Finally bodged a fix with some speedfit and flexible pipe. Not ideal but solved the problem.

All nice and rosy for the next 15 years…… UNTIL a week ago!! Got up to be greeted by the War Office saying there was no hot water. OK, out to the garage and sure enought the combi boiler (new 3 years ago) is showing a pressure of 0.2 Bar, below the cutoff at 0.4. Opened the filler valves to pressure back up to 1.4 Bar and all works OK.

Next day the same performance, after repressurising and using the system during the day all seems OK unless we go out for a few hours when same problem again on our return. Checked and bled all the rads, no air in the system. Goes down overnight every night now.

Got a heating engineer in today who thought it would be the PRV sticking but on breaking the union there was no sign at all of any water in the pipe so that is not the cause. He then puts on a doleful face and says I have a leak in the system! I CAN ONLY GUESS WHERE FROM.

The whole downstairs is the original concrete floor with new carpet in living room, very expensive solid oak in hall and dining room, ceramic tiles to kitchen /utility/

How on earth do I go about finding this leak which I am sure will be very small? When I find it what is the best way forward as I guess it will just happen again somewhere else?

When i 'fixed ' the first leak I was paranoid that I might have disturbed the pipe a couple of feet away under the concrete and caused anothe pinhole.

Any thoughts gratefully received, I can not begin to tell how depressing this is.

How do I stand with my insurance for which I have got plumbing cover?

Cheers,

Martin

[Martin King 2Participant @martinking2]

[Martin King 2Participant @martinking2]

Hi All,

I should add that the first leak was not on the heating circuit but was the cold mains feed to the utility sink.

It occurs to me that this one will possibly be agravated by the expansion/contraction as the heating system cycles?

Martin

[Gordon WParticipant @gordonw]

We had something similar in a bought house 30 yrs. ago. Did the same as you and dug up the floor, then moved. If I was you I would replace all the pipes below concrete with new laid above the floor, make some nice wooden boxes to hide them. Peace of mind is worth a lot. I have come across a lot of strange plumbing jobs. one of the worse was a house, new built, with a frost burst in the central heating. Some genius had put the pipes in the void between the brick walls.

[David JuppParticipant @davidjupp51506]

I presume the Heating Engineer did check the accumulator in the combi boiler?

I once helped a friend who had mysterious fault on the heating – like yours would work OK if topped up, but when cooled down over night was showing low pressure and wouldn't light. I eventually realised the accumulator was completely full of water (no air) – I found this by checking the Schraeder fitting on the accumulator. It was fiddly, but not all that expensive to replace. I presume the internal diaphragm had split.

You may well have a system leak, but it could be worth checking the accumulator before you start ripping floors up.

[Dennis DParticipant @dennisd]

You can get leak sealers for heating system from most large DIY stores or builders merchants. Do need to do a slight drain down if you have repressurised so that you can add it through the bleed valve on one of the highest rads. Did this a couple of years ago after having a similar problem and no trouble since.

[Alan Waddington 2Participant @alanwaddington2]

If there is no water coming out of the 3 bar PRV, then the expansion vessel is fine.

With the boiler switched off, check no water is coming out of the condensate pipe, (if it is then the heat exchanger is shot.)

Easy to check if leak is on system rather than boiler, just switch off isolation taps on flow and return under the boiler and wait 24hrs, if pressure on boiler stays up, leak is definitely on system.

Don't really recommend leak sealer it plays havoc with auto air vents etc and is a temporary bodge at best.

If one section of pipe is corroded chances are it will all be shot to some degree, concrete and copper don't do well together.

[Neil WyattModerator @neilwyatt]

> How do I stand with my insurance for which I have got plumbing cover?

If you have plumbing cover you are better off asking hem to investigate and sort it rather than starting a DIY and invalidating the cover.

Neil

[Martin King 2Participant @martinking2]

Neil, Good point, hadn't thought of that!

Alan, someone else told me that the leak sealers are a No-no. The 2 valves that you mention, are they the ones at the front bottom?

I pressurise the boiler by using two valves linked from cold mains on the wall, so do I assume that the valves you mention are permanently open? Then just close them for the 24hr test?

What is the correct method of putting copper pipes into concrete please?

Martin

[Steve PaveyParticipant @stevepavey65865]

Copper pipes should be in ducts of some sort. I think even sleeving in hessian is no longer advisable.

You have my sympathy – plumbers and electricians really take the easy way out when it comes to installation, and are still doing silly things like this – underfloor heating being a prime example, which has become very popular but is impossible to repair if a fault develops. Laminate and tiled floors don't help much either.

Really the only solution is to run new pipework at skirting level, or in the roof space, or bite the bullet and rip up all your expensive flooring. It might be that with some careful planning the pipes in the roof option is best, as you can often use one 'drop' to serve 2 or even 3 adjacent rooms, and conceal the drops behind curtains or kitchen units.

[Alan Waddington 2Participant @alanwaddington2]

Hi Martin

The majority of combis will have flow and return on the extreme left hand and extreme right hand 22mm pipes. But the pipe order is different on the odd combi, Vokeras for example are side by side extreme left.

easy way to be sure is run the heating and see which two pipes get hot.

The Iso taps are sometimes plastic handled affairs but some need a spanner or Allen key to turn

[Old ElanParticipant @oldelan]

Posted by Alan Waddington 2 on 22/10/2015 17:12:52:

Easy to check if leak is on system rather than boiler, just switch off isolation taps on flow and return under the boiler and wait 24hrs, if pressure on boiler stays up, leak is definitely on system.

With the boiler turned off, of course.

[MuzzerParticipant @muzzer]

The expansion vessel usually has a fairly small volume like a litre or two. Each time you fill it up to 1.4 bar and let it leak down to 0.4 bar, you release the best part of that volume, so until you figure out where the leak is within the CH loop, you should stop refilling it. Or I suppose you could put coloured dye in and go for the scientific approach

Doesn't sound as if you have much of a clue how pressurised CH systems work – nor your plumber for that matter – does he double as the village idiot? Try to find a plumber who actually has some level of understanding. Isn't there a "find a tradesman" scheme with which.co.uk etc? It's not exactly rocket science but if you carry on like this, you will simply compound the problem.

Murray

[Alan Waddington 2Participant @alanwaddington2]

Posted by Old Elan on 22/10/2015 20:02:03:

With the boiler turned off, of course.

You would still be able to use the boiler for hot water, but of course turn the heating to "off"

[Alan Waddington 2Participant @alanwaddington2]

Once had a similar situation in a very posh house that had the downstairs floors fully tiled in very very expensive tiles.

The owners hired an outfit with a thermal imaging camera to pinpoint the leak.

Worked a treat, and only one tile was harmed in the fixing of the offending pipe.

The tilers had used nails that were 6mm too long to ply the floors prior to tiling and despite using thousands of the buggers they only hit the one pipe.

Camera team cost in excess of £500 though !

[Enough!Participant @enough]

Posted by Alan Waddington 2 on 22/10/2015 20:39:50:

The owners hired an outfit with a thermal imaging camera to pinpoint the leak.

Camera team cost in excess of £500 though !

Wonder if one of these would help

[russellParticipant @russell]

search for ultrasonic leak detection – apparently the water escaping makes a noise….

-russfromOz

[Les Jones 1Participant @lesjones1]

One place where a leak will not be seen is on the heat exchanger in the boiler. If water leaks from there it will not be visible as it will just go down the condensate drain. My sister had this problem on her central heating. We had checked all the pipes fo leaks but did not find any. If you have shutoff valves on the flow and return at the boiler you could use the following method to see if the leak is within the boiler or in the pipe work. On a radiator (Preferably upstairs.) make an adapter to connect a pressure gauge to the top blanking plug. Drain a reasonable amount of water from this radiator. Close the vent and re open the two valves on the radiator. Now re pressurise the system. Close off the flow and return stop valves at the boiler. Note the reading on the pressure gauge fitted to the radiator and the one on the boiler. With the boiler turned off leave it for a few days. If the pressure gauge drops on the radiator then the fault is on the pipework. On my sisters boiler the leak only occured on the heat exchanger when it was hot so the pressure gauge on the boiler did not drop during this test. The reason for draining some water from a radiator is so the air in it acts as an hydraulic accumulator.

Les.

[Martin King 2Participant @martinking2]

Hi all,

The saga goes on!

turned off the heating, pressurised system to 2.4 bar and shut the feed and return valves to the heating loop.

Next morning pressure the same, so I guess there is no problem with the boiler.

Damned if I can find my insurance policy so company is sending me copies, have not said a word to them yet.

What does the team think is the best way to approach the insurance people in this situation?

If they get the thermal imaging people in to find the leak, dig up the bit of floor, fix leak and make good floor, I am left with the highly likely possibility that it will happen again somewhere else which is not really acceptable.

Will they stand for replacing all the ground floor pipe work in the concrete or will they want to run surface pipe work which is REALLY unsightly and not what we want?

My wife is adamant that nothing is going to happen before Xmas so will have to keep topping up each day, is there any danger/ problem in doing this?

Does anyone have any experience of the type of skirting that can conceal pipe work?

Questions, questions! Any help much appreciated, this is a nightmare!

Martin

[Clive HartlandParticipant @clivehartland94829]

Some years ago a lot of central heating systems were made with small bore pipes, perhaps you could utilise this method to replace the hidden pipes. They would, due to size be inconspicuous. My first thought is to abandon the entombed pipes that are in the concrete floor. My experience of underfloor pipes in a business building was not good as they were plastic and they were penetrated at least twice a year by people drilling into the floor to secure racking.

Clive

[Alan Waddington 2Participant @alanwaddington2]

In my experience the insurance company will only pay out for any damage caused by a leak, not for repairing the leak . Unfortunately i suspect you will be on your own with finding and repairing the problem.

If i were you i would be thinking of replacing the whole lot, either by cutting new channels in the concrete ( messy) or surface mounting (unsightly)

There are some commercial concealed skirting systems available, but it might be as easy to break out the woodwork tools and do your own. 10mm speed fit pipe is arguably easier to hide than copper. Its a lot of work though if you want it to look good. And you will probably encounter the odd doorway etc that presents a routing obstacle.

Quite often concrete floors are quite soft and making new channels might not be as difficult or messy as you imagine. Only a test dig will tell you.

Alan

[wendy jacksonParticipant @wendyjackson]

You need to find the leak. from reading what you are saying, it looks like the old repair as gone again. did you concrete in the pipes again ??? have you tried a damp meter to find the leak ???. if the leak is in the same location, dig out and renew the pipe run. Place pipes in channel to protect them from the lime content of the concrete. michael

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