How do I detect leak in heating pipes under a concrete floor

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Sorry....but this is yet another question about loss of pressure in system.

I had my central heating boiler replaced in May with a worcester bosch boiler and currently having to top up the pressure twice per day.
I top up to 2 bar and within about 8 hours it is back to 0.
This drop from 2bat to 0 equates to approx 2.5 litres, so if I am topping up twice a day, thats 5 litres of water going somewhere.


The installer (Chris) has been back 3 or 4 times and cannot find anything leaking above ground. This is a bungalow so have checked loft, all rad valves and been down on our hands and knees over all carpets to try to find a damp patch. Also, no sign of any damp on walls.

The rooms all have carpet or laminate floor on top of a concrete floor. The pipework is in the concrete floor itself, and not in a channel infilled with a sandy cement.

We have tried Fenox leak sealer, but that has been in for over a week and has made no noticeable difference.

I have ready hundreds of posts regarding loss of pressure and most of them end up with the leak being found pretty easily.

The old heating system was not pressurised, so this could have been leaking for a long time as the header tank would have refilled it without us knowing.


So, the reason for this post is..........has anybody got any ideas of what else we can try?
Can we hire a device to detect this size of leak without lifting carpets and digging up floors?


any suggestions would be gratefully received.
Thanks, ian
 
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Lift the carpets and underlay up and you'll see a stain somewhere. For the laminate sections, remove the joining strips between rooms and wedge a metal bar/rule under the laminate to tease it up (without splitting!) so you can get a torch beam under there. If you see a damp satin, obviously, it'll all have to come up.

Sometimes you can feel a warm patch on laminate - walk over it barefoot, but this can be misleading, as it may just be a union that's closer to the surface.

Edit to say: If it's leaking under the laminate (as it did with me), the membrane will contain the water and damp smell.
 
Are you sure it's leaking from the pipework? From what I've read, the symptoms you mention could well be caused by a faulty or undersized expansion vessel. If you try turning your CH/HW, top up to 2bar and then check the pressure the next day and it has not dropped then that would further the above theory, as there is no thermal expansion taking place.

When the system is running the hot water expands, the only place it has to go is the expansion vessel, and if it can't go there then it'll escape into the condensate drain on the boiler through the pressure relief valve. As soon as whatever water is left cools down again its volume decreases, and you've got no pressure any more.
 
Could only have started leaking since upgrading - with the increased pressure from the sealed system it can start leaks where previously all was ok.
 
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If you have gone from un-pressurised to pressurised could be the coil in your old copper cylinder leaking to your hot water side(DHW)?
Do you have a System boiler?

If your plumber ripped the cylinder out to fit a combi (no stored water)instead forget my suggestion!
 
Thanks for the replies so far....

Some answers to the questions posed:

The hot tank and coil were replaced as part of the job.
The pressure goes down to 0 after about 10-12 hours even if the HW is switched off.
Have also checked condensate drain and pressure release pipe (whatever its called) and nothing from either of them.

When the new system was installed, it all seemed to work fine for about 5 days and we had the heating on then too just to test it out. Only after that initial 5 days did the pressure start to go.

Thanks
ian
 
Is each radiator on storks that drop down in your loft??

If so get onto each stork that supplies the different radiators and isolate them by fitting iso valve. then isolate a rad at a time.. or you could just re-pipe above ground and pen-doc
 
then if you isolate each one you can find which section of pipe work its on but the amount of water could be multiple leaks!!!
 
Thanks for the replies so far....

Some answers to the questions posed:

The hot tank and coil were replaced as part of the job.
The pressure goes down to 0 after about 10-12 hours even if the HW is switched off.
Have also checked condensate drain and pressure release pipe (whatever its called) and nothing from either of them.

When the new system was installed, it all seemed to work fine for about 5 days and we had the heating on then too just to test it out. Only after that initial 5 days did the pressure start to go.

Thanks
ian

How about your plumber injects a stain into rad water to make ANY leak apparent. If its the coil you will then see it mixed in your hot tap water. If not, you should soon see where its coming from. Drastic fault, drastic measures!
 
Forget leak sealer, it doesn't work on any hole bigger than an ants d**k :LOL:

I have had 2 or 3 systems that have unfortunately ended up with leaks under the concrete/screed floor with absolutely no signs of the leak under the carpets :(

Are you 100% it's your system and not on the boiler?

If so you have 2 unfortunate choices.

1) start digging up the screed to try to locate the leak
2) re-pipe your ch system, not using any of the existing pipe work.

Option 2 is the one I have always been asked to do by my customers.

Unfortunately there is no 'magic wand' solution for your seriously frustrating situation.

Or to quote a very rough and basic saying, 's h i t happens' :eek:
 
more answers......

The boiler is in the kitchen and all radiators are on the ground floor (as it's a bungalow). All pipework for radiators are under the concrete and there is no way to see if there are sections that we could isolate.

Not too keen on the idea of stain in the water untill I have tried everything else as carpets are relatively expensive.
Somebody suggested a litre of strong cheap perfume. Put that in the system and see which room the smell appears in.

Surely there must be some sort of meter or device that could be hired to detect the leak? There must be something that Damp people use.

Alternatively, would it be possible to convert the new boiler to open rather than pressured? It may be cheaper to do this than start digging up floors.


thanks again
ian
 
I wouls disconnect the downstairs heating and see what happens, if pressure holds in upstairs and h/w have the ground floor re-piped.
 
Changing to an open vent boiler wouldn't cure the leak, only stop you having to keep pressurising it your self. The F&E ballvalve would just keep opening and top up the constant leak :eek:

You could pressurise the system to test for leaks, but this will not show you WHERE the leak is, just confirm you have one.

Unfortunately back to my last posts 2 options I'm afraid :(
 
If the pressure drops to zero, the damage is done - reverting to open vented will still leave it leaking.
Doesn't sound like theres any choice but to repipe it all, unless if the new cylinder is vented - does it still rely on a header tank in the loft to fill the cylinder - if it's vented, the new cylinder could be faulty and letting your heating water through into the hot water part of the cylinder - if you use the hot tap every day, chances are any overflow from the level slowly rising in the header tank feeding the cylinder would never show up.
Edited to add water diviners find hazel twigs work best :oops:
 
nahcartsnai
if you could isolate heating runs from rest of system & pressurise it to at least 4 bar with a proper pipe tester for 10 mins at least you will know that you are going to find a leak if pressure drops if it does pump up pressure more and it may show on bare screeded sections
 

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