Why is my hidden copper piping so wet ?

[Richard33]

Hi,

I've copper pipework in a concrete floor that's been down approx 8 years. My oak floor started to cup/lift so I've dug up a patch of screed, down approx 5 inches to the pipe work.
The pipes were adequately wrapped in plastic backed felt, laying on top of the dp membrane with an off cut of membrane on top, followed by sand then screed. There are the cold & hot pipes and the 2 ch pipes close together. When uncovered the felt had turned black and completely soaked and smells of a stagnant pond. The sand also was very damp. Is this a classic leak or can condensation from the cold water pipe cause this ? Also if not a leak what can I do ? re run the cold above ground ? I think the wetness has travelled all along where the pipes run as the floor has cupped in line with the pipe run. Thanks in advance

 

[Agile]

You need to consider or test this by pressure testing the PIPES for leakage!

Its usually a failed soldered joint.

Messy/hard work to repair too.

Tony

 

[Richard33]

Tony, thanks. The system is a pressurised hot water system. I'm presuming as the pressure gauge for the ch is unchanged and I've not topped up from the mains for over a year this is sealed and fie. I'm guessing the leak if this is the case is in the hot or cold feeds to the kitchen sink,washing machine etc. The ground is soaked so can condensation sealed in concrete really happen to this extent ? As usual the insurance Co want you to find the leak and fix it before they will agree to pay up ! Thanks again

 

[Agile]

Dont expect an insurance company to pay for repairing leaks.

They will usually pay for consequential damage though.

Tony

 

[Richard33]

Thanks - yes they have already said find the leak and fix it then they will pay for the ruined oak floor.
Last question if I can - I presume condensation in this instance is very unlikely however I'm just paranoid of digging up all of the floor and not finding a leak. If this is the case any tips on how to prevent condensation in future ?

 

[Bahco]

Repipe so that your new pipes are ABOVE ground. Quite regular to have people come on this forum with buried pipe problems.

Do it properly and you will have no further problems yrs down the line

 

[Agile]

I find that over 90% of the leaks are at the elbow between the horizontal and vertical pipe to a rad.

Tony

 

[Red_Man]

It will not be condensation.

 

[Richard33]

Thanks Red Man / Tony. There's no pressure drop on the ch (been at 1.5 for over a year) so I'm sure the "leak" is in the hot or cold run. Can I presume any plumber can perform a pressure test or do I need a specialist ?

Red man can I ask why you are so sure it's not condensation ? is it as condensation doesn't occur in a concrete floor with the pipes lagged and surrounded in sand ?

 

[dextrous]

Any plumber, or even diy-er can perform a pressure test using a wet kit.

If you can determine where the pipes enter and exit the concrete floor, then you may be able to test the embedded sections of pipe. This will at least determine whether condensation is a goer (I doubt it) and which pipe has failed.

 

[Richard33]

Thanks - if a leak I'm pretty certain what run the leak is on - there's a 4 metre length. Daft question but do you need to cut any pipes to run this test ? looks like I'll be asking a plumber to do it !

 

[Agile]

If its not a heating pipe then I find its usually a hot water pipe because the constant heating/contracting thermally stresses the joints.

Tony

 

[dextrous]

Thanks - if a leak I'm pretty certain what run the leak is on - there's a 4 metre length. Daft question but do you need to cut any pipes to run this test ?

It depends - one end of the run will need to be capped off (but there may be an isolator tap somewhere to facilitate this, and the other end needs to be connected to the testing kit. Since there will be compression joints within the kitchen already in place (for tap and washing machine connections), one end will be easy to deal with. It's the other end (entry point into kitchen) which may require a bit more thought/work.

 

[Onetap]

It will not be condensation.

Yes, it could be condensation on the cold pipe. There is no vapour barrier, water vapour will permeate through the floor, condense on the cold pipe and saturate the floor structure. It could be a leak though.

The hot and cold water services (not the CH) should have been installed in sleeves or a duct to allow the pipe to be removed, required by the Water Regulations G7.3.

 

[Richard33]

Thanks onetap
The fllor is a concreate block and beam to suspended off the ground by a good foot. There is then a blue dpm with the lagged pipes on top of that. Then off cuts of the dpm covering the pipes, then a layer of sand 3-4 inches to aid movement then a final layer of screen. Effect of saturation is bad and has obviously been going on for years due to the stagnant smell when uncovered and the black mess that was once the lagging. I think the oak floor has decided to cup/warp/lift this winter due to continuous heating being on and extra cold mains water. Given this set of circumstances could this cause a "sauna" affect underground ? Damage to floor is worse where the pipes were run but now spread across the rest of the floor but in those places there was polystyrene insulation in place of the sand.