Pipe Leak in Solid Floor - Suggestions Please

Hi all
OK so now I am well passed the end of the old teather! Bought house in 2002 and discovered that damp patch in dining room was not due to patio door problems but a leaking pipe in the solid concrete floor. So broke out top of channel and repaired leak in hot water feed for the existing kitchen extension. The damage was a broken elbow that had obviously been leaking a fair while due to limescale build up on the face of the fitting. The elbow was replaced with a formed bend for better flexibility. The floor was left uncovered for a good while and the top of the slab appeared completely dry. Last year we decorated the room and finally got carpet down. Over the weekend I noticed a raised bit of floor toward one corner, peeled back the carpet to find that some infill concrete has "blown" due to damp and there is a film of water on the bottom of the underlay.
So the questions are:
Has anyone had serious leaks into a concrete floor? Could the appearance of water be a result of the CH driving previously leaked water to the surface? How can I find the source of another leak if there is one? I cannot hear water running when all taps etc are off. The CH header tank does not appear to drop significantly if the ball is tied up. Within the dining room floor there are CH flow/return pipes, hot (gravity fed) and cold (mains fed) water to the kitchen.
Any suggestions on means of locating/testing for leaks would be appreciated. The fact that the room is the most recently refurbished makes me reluctant to start hacking up floors/destroying box work etc. SWMBO has not yet been appraised of the issue!
Final question:
Should insurance cover this? No plumbing work has been carried out in the last 2 years!
TIA
Phil
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
TheScullster wrote:

When you repaired the pipe, did you then simply re-fill the hole with cement/concrete? Was the pipe protected in any way either originally or in your repair?
Is there any possibility of bypassing that leg of pipework? Maybe using a completely different route? Maybe using plastic pipe would make a route viable that was not sensible when the extension was built?
Are you certain of the route the entire pipework takes through the concrete? I would hazard a guess that if one joint has failed, any others that exist could also fail and would not wish to trust any that might exist. If unprotected, I would not even wish to trust the straight, unjointed pipework in the long term.
--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Rod" wrote

The pipe was carefully wrapped in dpm material before concreting over. Originally, the u/ground piping is all wrapped in a hession type sleave in a channel of sand.

Yes that is possibility which I have made provision for, but I'm not sure if that pipe is leaking elsewhere or not. It might be another pipe that is at fault. Or maybe there isn't a leak there now and the moisture that is surfacing is water from the original leak that is trapped around/under the slab. The problem is, how do I confirm what's what?

Phil
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you dont want to dig up the floor or bypass all buried pipes with surface plumbing, you might put some dye in the CH primary. I'm guessing it would take a fair while to know if that dye had come through the floor or not, so not exactly a quick solution, but certainly an easy option - in a month's time you'll know what to bypass and what not to.
You may well find that the rubber underlay has stopped the leaking water from evaporating from the slab, and that using porous flooring leaves the slab dry to the touch, once its dried off initially.
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

in
a
a
if
is
others
Hey Scullster, face it mate. The only sure way to find out what's what, is to dig it out and have look. What damage has been caused by this problem? Ask your insurance if they will cover it, before you go digging it all out.
Once you fix what ever it is, it seems that the protection methods currently being used are not up the job. When the fix has been done, try boxing around the pipework with loft lagging and sand, before making good the floor.
How deep are the pipes in the floor? Is the room heated throughout the night? What composition is the floor, and is it laid directly on the groundwork? How close together are the pipes? Can the cold feed use residual heat from the central heating runs to keep it from freezing?
The best underfloor system I've seen, was a trough containing the pipes, a layer of sand, a layer of loft lagging, pipe runs, a layer of lagging, and topped off with narrow paving slabs an inch or two below floor level, then skimmed over to make good. So the pipes were not hard packed in the floor at all. Amazing that it still has no problems after thirty years of continuous use under our workshop floor. I have also seen it done with brick capping and it has had no problems for years also.
Something could be wrong with the pipework in the floor, and you'd better get is sorted or it is going to recur. It may take three years the next time, but what if it happens again. Get it fixed with at least a 20 year guarantee on it.
Good luck with it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
BigWallop wrote:

Be sure its not merely a concrete slab lying on wet ground with no membrane under.
But yes, dig the bastard up.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

How much, if tied up for a week or 2, how much does the level go down?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Can you not isolate each pipe in turn and pressure test it with a car pump and a pressure gauge bought for the purpose from Screwfix?
http://www.screwfix.com/prods/72940/Hand-Tools/Plumbing-Tools/Pressure-Test-Equipment/Monument-Dry-Pressure-Test-Kit
You would then be able to verify the integrity of the pipework without digging up the floor - providing you can find somewhere to connect the gauge for each of the pipes you mention (CH Flow and Return should be achievable, DHW should also be possible, Mains cold water feed may be a bit more problematical).
A bit of tinkering here and there to boxing in is a hell of a lot less work than digging up an entire floor.
I would be very surprised if the current damp problem is caused by previously leaked water being driven to the surface, simply due to the sheer volume of water involved if, as you say, the underlay is literally wringing wet.
I wouldn't rule out the possibility that the dampness is caused by an entirely new problem.
Luke
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Running a surface pipe is a fair bit less work than digging it up.

quite.
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.