Internal Wall Damp - Advice Please :)

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Hello folks!

I have a minor damp problem on a downstairs internal wall of our 1986 property.

I was clearing the wall to make way for some cabinets when i noticed the damp had affected the skirting board i chopped out. This was apparent across both walls that meet at the corner in the 'wet side' pictures i have uploaded.

As you can see, some of the copper is new. The plumber who installed it suggested that it might be a crack in the waste water downpipe on the other side of the wall that was causing it. I remembered that there was an inspection hatch on the boxing, so i inspected and found it to be pretty dry in there (there was one small dark patch away from the pipe). Other than that, it seems to be bone dry in there (despite the wodge of silicone used at the clay / plastic interface!)

I have included photos of both sides of the wall, hopefully these provide some context.

The white waste pipe on the 'wet side' pics (featuring copper) goes through the wall and connects to the large grey waste pipe on the dry side. You can see this connection on the pic named ‘dry side’.

There is a toilet room on the other side of the wall which the white waste pipe is attached to. I have some white, vinegary smelling deposit coming through the grout between the floor tiles in there. I cannot work out if this is connected or a separate problem as it is close, but the white deposit does not run all the way up to the offending wall (I suspect it is connected).

Can anyone suggest a course of action that doesn’t involve ripping up tiles and shower trays ( I realise this may be required, just trying to eliminate other options first!)

Many thanks!
Ewan
 

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The copper pipework appears to be just below the surface of the floor tiles, pressure from walking on them may have caused a leak at the nearest joint i.e. the wall. The new pipework may or may not solve the problem in the long term

You may be unlucky and also have a cracked clay waste pipe as your plumber suggested. If that is ongoing it is more of a problem than just drying out what damp remains.

These are just my observations as a DIYER

Blup
 
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Thanks for your reply Blup! This isn't drying out unfortunately. I had considered the pipes leaking under the floor, but don't know how to diagnose it. If I knew where the other end went, I suppose I could fire some air through it, see if pressure dropped when one end is blocked?

If the clay was cracked, why do you think the evidence is manifesting itself on the other side of the wall? I am no expert on leak propagation, would love to understand it a bit more so I could try and diagnose it properly!

All comments / help gratefully received!
 
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I have a horrible suspicion the copper under the floor may be the issue. Copper reacts badly with cement based products, and will corrode if not suitably protected. Might only be a slight weep under there but enough to cause a damp issue.

You said the Plumber has just installed the copper, what does it feed/come from?
 
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Just an anecdotal experience - Had a house a long time ago rented with a copper pipe running under the concrete kitchen floor and persistent damp in the cloakroom behind the kitchen. The water company switched to a meter and the tenant rang to say they had a £1000 water bill come through o_O had the buried section of pipe bypassed instead of digging up the floor. If water pipes are buried tend to use plastic now
 
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If you know a young person with sharp hearing, get them to stand near the suspect area late at night when all is quiet, while you repeatedly turn the pavement stopcock on and off. The sound of a leak is just faint white noise, but you notice when it stops and starts.

Or use an Engineers Stethoscope.
 
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I have a horrible suspicion the copper under the floor may be the issue. Copper reacts badly with cement based products, and will corrode if not suitably protected. Might only be a slight weep under there but enough to cause a damp issue.


You said the Plumber has just installed the copper, what does it feed/come from?

Thank you very much for the replies folks!

Nice name Hugh ;) This was my suspicion as well, the damp is too localised to be coming from anywhere else in my unprofessional opinion!

Djks, good point, I think I know roughly where it is jointed from - the kitchen sink. It is a crazy route if that is the case, as there is 20ft between the boiler and kitchen and the leak is about 6ft from the boiler - so a 40ft round trip from a boiler 6ft away! Running some pipe from the relatively new hot/cold supply in the loft is my best bet I think.

John, Awesome tip, I never thought I would be able to hear a leak like that, I will give it a try!

I like the fact that no one is pursuing the waste pipe as being a potential source. I will try and rule out / confirm the copper option before getting a camera man in to inspect my drains!

Genuinely, a massive thanks to all, really appreciate forum wisdom :D

Keep the good ideas coming please!
 
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I was curious to know where the pipes came from/went to, is the flow coming from under the floor or going the opposite way? If the flow was going under the floor then I'd try putting Isovalves in between the clips and the elbows, shutting the flow off and seeing if things dry out a bit. Pipes looking rather green where they enter the floor, never a good sign. Does the felt sleeving feel damp?

Also worth noting, whoever has fitted the Tee in the waste pipe, with the taped off end, it's the wrong way round....
 
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If the flow was going under the floor then I'd try putting Isovalves in between the clips and the elbows, shutting the flow off and seeing if things dry out a bit.

This was exactly what i thought, confirm feed, isolate supply, see if it dries at all By isovalves, do you mean the screwdriver operated valves fitted at sinks / toilets? If not, what do you mean buddy?

The hessian / cloth insulation is indeed damp and the copper is corroded where it dives below the floor tiles.

Would clean water cause the white deposits on the grout, or would this indicate waste water with dissolved soaps etc?
 
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I think you've answered you own questions here.... Isovalves, yes the 'Ballofix' type used on sinks etc would be ideal, just to prove a point. If the copper is corroded where you can see it, then that doesn't bode well for it's condition underneath. Had it happen myself in my own house, copper I sleeved and laid under a screed floor began to leak about 6 years later, still to this day I dont know why, it was protected in the correct manner. When I dug the floor up to remove it, the copper was so corroded, it broke up, like rusty iron pipe would do. Replaced it with plastic pipe in a duct for future proofing!

Waste/soil may have a slightly more pungent smell is its leaking, but bear in mind the stack/waste will only have water in it when something is discharging, and never any real pressure unless the drain is blocked and its backed up.

Clean water could easily cause the deposits as it lifts dissolved slats etc out of the material used to construct the floor.
 
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