Leaking underground pipes.

[rccatnap]

A friend of mine seems to have a leak in his central heating pipes that are under concrete. He has to pressurise the system three time a day to keep the heat going. He realises that some foundation(s) will need to be dug up to facilitate a repair, but is there a way, electronically or otherwise, to locate the source of the leak?

[The Builder]

Are you sure it's a leak? Leaks in pipework under concrete or floor screed, usually show up as a damp patch.

[old-wos-is-name]

whats been laid on top of the concrete floor, is it carpet or laminate flooring etc?

[rccatnap]

Both carpet and laminate. There is a constant hunt for damp patches, but none have appeared as yet, even after several weeks. There are no leaks around the boiler at all. Thank you both for your input.

[The Builder]

It might be an idea to have the system drained and then pressure tested. It's a simple hand pump-up device with a gauge that will indicate if a leak exists.
It doesn't tell you where though. For that, there are all kinds of specialist devices including ............. microphones for acoustic tracing; imaging; and easiest for you ......... tracer gas to pinpoint it exactly.
Usually specialist companies provide this, but you might be able to rent the gear.

[AlBags]

If it is a leak underfloor .. and not too far from point-of-entry .. that is where it will usually show up .. point of entry. It rarely just soaks away.
Have you checked the pressure vessel?
Have you looked at the relief valve for leakage (bag or condom over outlet pipe and monitor)?
(TB has some spare ones)

[rccatnap]

Many thanks for your advice. I'll tell my friend and see what he wants to do.
Happy Christmas and a healthy New Year to everyone.

[chas2008]

i have gas pipes running under concrete and i always thought if there was ever a leak the floor would need digging up, wrong!! Logically all you need to do is re-route the pipe above the concrete,just leave the original pipes in situe..not sure if this would apply to the above post but worth considering and probably cheaper with far less hassle.
Just think of how they would fit a c/heating system in this property if it never had one, certainly wouldnt be ripping concrete up...

[buildersmate]

Chas, I fear that you misunderstand the point about routing pipes for UFH in concrete. The pipes are specifically embedded in there such that they heat up the concrete sub-floor and the heat rises into the room. There are tens of metres of the things, coiled up under the floor like a serpent.

rcc - one thing you can do to eliminate some area of the circuit is to pressure test the individual UFH zones (which I assume you have) - mine has six different zones in the ground floor concrete. Do this from the manifold (where the actuators that turn the individual zones feed from / return to.
That at least tells you which zone is leaking.
Whose make is the system? Leaks once installed are very rare and are either caused by:
1) SEVERE movement in the concrete slabs that have split a pipe by stretching
2) mechanical drilling into them above above - for example, when (unwisely) fitting door thresholds by drilling into the floor
3) (very rare nowadays) examples of inappropriate pipe used in the installation. This degraded over a period of time but the splits generally occur close to the manifold on the onward leg of the heat transmission.

[AlBags]

TBH .. The original question was not very clear.

Complete difference in system pipe-work ..

Heating pipes under the floor with rising tails to radiators ..

Or ..

Under-floor heating system.

[buildersmate]

Ah - see what you mean Al. I was thinking UFH.

[chas2008]

aha, underfloor heating..........

[chas2008]

wonder which it is, the mention of foundations got me to thinking normal c/heating...

[AlBags]

... when what they meant was .. under the slab/screed (floor) : )

[chas2008]

and the post title 'Leaking underground pipes.

[rccatnap]

Thank you all for your considered answers. As I mentioned in the first post, the problem belongs to a friend of mine. I do not know all the particulars of his heating system, whether underfloor heating, radiators, or a combination of both. The title by its very nature was intentionally vague purely to encourage some lateral thinking in the AB members and that indeed has been the case.
I shall now pass all your comments to my friend for him to decide on his course of action. Thank you all again. I shall now consider this subject closed, but will come back later when the problem is solved. Happy Christmas to you all.

[rccatnap]

Problem Solved.
My friend took 'The Builder's advice and got in a specialist company.
The system was first pressurised (again) and the central heating turned up fairly high. A thermal imager was used to ascertain the exact location/run of all underground pipes and the upper floors. The system was then drained and a gas mixture of 95% nitrogen + 5% helium pumped in. A sniffer probe was passed all along the known pipe runs. It was very sensitive to helium which would, if present, pass through concrete and laminates etc. for it to be sensed. The culprit finally turned out to be the drain valve in a small radiator in the downstairs toilet. It was leaking very slightly, so slightly, that the water evaporated before it could accumulate enough to be noticed, but enough for the pressure drop to affect the heating. The workers were on site from 09:00 to 19:00 and including replacing the whole radiator, it cost about £350. My friend was well pleased that no floors needed to be dug up.

[gunnersvicky]

Hello who did your friend use as we have exactly the same problem and our quotes just to find it are £850!!