Damp patch on concrete near to pipes

[absolute0]

We've recently had a new kitchen installed - Yay! , but have found a damp patch on the concrete floor - Boo

The damp patch is located just in-front of the hot & cold water feeds, which are buried under the concrete. The pipes have been there for about 25 years (part of an extension), and we've only been at the property a couple of years and only just noticed the problem. We've had our builder inspect the pipes, which are wrapped, and the wrap/lagging material is dry where the pipes come up out of the ground (and down to about 1-2 inches). He felt that it is unusual for it to be the pipes as the wrap/lagging would be soaking wet, which it's not.

We dried the patch out this morning, but within minutes the patch returns (see pictures). There aren't any other signs of damp patches elsewhere.

Any advice on this is greatly appreciated.

Dried:

Dried out patch

• absolute0
• 23 Sep 2015

After a few minutes:

Not so dry

• absolute0
• 23 Sep 2015

Damp patch reoccured:

Wet patch

• absolute0
• 23 Sep 2015

 

[JohnD]

have you got a water meter?

I can see about five pipes there. Wrap kitchen roll tightly round each of them. See which one the water is coming from.

If you are lucky it will be a joint.

 

[Burnerman]

If there's no obvious dampness around those connections, I think that concrete has to come up, unfortunately.
John

 

[absolute0]

It's definitely not the connections, checked these and they are all dry, unfortunately.

Yes, on a water meter.

I can't understand why it is isolated to one area though? Assume it could be a small leak in one of the two pipes?

We did have a new combi boiler fitted a couple of years back. Could the increase in pressure cause this?

 

[JohnD]

turn all the taps off, and observe the water meter. Does the central bubble always keep turning?

If so, and you turn off the water at the boiler, does it stop?

 

[ree]

1. What occupies that space - an appliance, a unit etc.? Whats happening outside the pic on the right hand side?

2. The upper joint doesn't appear to have been properly made, and the pipe is possibly under tension pulling down? FWIW: i would take those fittings apart and remake them making sure that the pipes are not under tension, & the plastic pipes have inserts.

3. There seems to be a rim of soil(?) below the neighbouring unit?

4. the light toned patch on the concrete surface possibly was an actual patched area made good?

5. Can you shine an inspection light under the unit from the front plinth and take some pics from the side panel notch?

6. where are the copper pipes coming from - across the field of the slab or hugging along the wall?

 

[geraldthehamster]

From the progression in the pictures, it does look as though the water is rising up through the floor.

Cheers
Richard

 

[absolute0]

Apologies for the tardy response and thanks for everyone's replies.
I've had a plumber in today to dig up the pipes as that seemed like the best way of checking.

Appears that it was a slow leak caused by a hole/dent in the pipe on the hot feed. It wasn't where we expected, but due to the slope on the pipes think this is where it was surfacing. They uncovered the concrete near the damp patch and then followed it back to find more water. Water erupted as they uncovered more concrete nearer the source.

They have replaced the copper pipe with plastic. It now needs to be left to dry out.
I am a little concerned with the exposed copper pipes left (no wrapping) and the stress applied to the joins under the cupboard (see pics).

I'm not used to plastic pipework, is this acceptable or should it be re-done to reduce pressure/bend on elbows?
Can anyone recommend what I should use to fill in the trench?

Pipe work black and pitted, source of leak:

Exposed pipe

• absolute0
• 14 Oct 2015

New pipe fitted:

New pipe

• absolute0
• 14 Oct 2015

Join copper to plastic:

Join

• absolute0
• 14 Oct 2015

New pipe 2

• absolute0
• 14 Oct 2015

Pipes under cupboard (appear to be under stress)

Under cupboard

• absolute0
• 14 Oct 2015

 

[ree]

Nothing about them pics says professional plumber - they shout DIY job.

As it is you will most probably be digging it up again whenever.

 

[geraldthehamster]

As it is you will most probably be digging it up again whenever.

I agree. I wouldn't be burying plastic fixings in a concrete floor. In fact I've just replaced something similar - a PEX pipe had a push fit connection to a copper rising main, in the floor, done as temporary fix to move a stop cock when removing a wall. I replaced it with copper tube and a proper soldered joint.

Copper tube running in concrete should be wrapped in Denzo tape or pipe lagging, as concrete corrodes copper.

In the cupboard picture, the pipes coming from bottom right look as if they have been cut too long. Some of the curvature in the horizontal pipes may be how they came off the roll, but you can see the strain on the connector attached to the vertical pipe that disapppears upwards, so it's all being pushed up.

Looks like you have a job by a cowboy tradesman, rather than a proper DIY job

Cheers
Richard

 

[absolute0]

Thanks for your feedback on this, really appreciate it.
I would be happier putting copper back in with a proper soldered joint & wrapped. Then the pipes would come in closer to the wall and the fittings could be done correctly.
Just need to find a decent plumber to do the job now

 

[absolute0]

Managed to get a decent plumber in to rectify the areas that I was concerned with. So all good now, thanks. Still have a PEX pipe in place as this was preferred.

Now that it is all dry & no further leaks I'd like to screed over.
Would a 4:1 mix of sharp sand and cement serve to fill in the trench that I have in my floor?
I've read that it shouldn't be wet, but not overly dry either. Can anyone advise please?

 

[geraldthehamster]

Did you manage to use PEX pipe without the need to bury push-fit connectors under the floor?

 

[absolute0]

Unfortunately not.
Does that affect the screed used?

 

[geraldthehamster]

Unfortunately not.
Does that affect the screed used?

No, it's just a really bad idea to bury push-fit connectors in an inaccessible location, in case they leak. Hence my recommendation to use copper pipe and soldered joints.