water leak behind interior wall

Old 01-16-06, 01:04 PM
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water leak behind interior wall

I experienced a "small" leak about a month ago in an interior wall between a bedroom on one side and bathroom sink on the other. I first noticed the carpet being damp, so I pulled the carpet back and found the foam rubber pad was damp on the underside but not on the top. The carpet appeared to be "wicking" the moisture and had a damp place about 3 foot square. I let the carpet, foam rubber pad and the floor dry completely. I did not use the sink again until it was dry. After about a week I used the sink to see if the floor got wet again and it did. I again let the above items dry and used the sink again. Once again the floor got wet. I did this to confirm that it was a drainage side problem and not a pressure side problem. All the while, I had left the foam rubber pad and carpet pulled back to keep them dry. I openned the drywall and exposed the plumbling for the bathroom sink and nothing appeared to have gotten wet, except a small piece of flat metal nailed to both sides of the shoe plate where the PVC goes into the concrete slab (used to keep someone from driving a nail into the PVC piping). Now I'm trying to fix the leak and can not dupicate the problem. I ran both the cold and hot water for an extended length of time but find no moisture at all. I did this several times and still no leak. What's up with this? I had the house repiped about 6 years ago. I've been in the attic and do not find any evidence of moisture anywhere up there. Please let me know as soon as possible. I'm going to be installing wood flooring and thats suppose to start tomorrow the 17th.
Old 01-17-06, 06:18 AM
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It sounds like the water is coming from that drain pipe where it enters the slab, or just below the slab. You could confirm that by taking some rags and tie them around the pipe in the wall: right at the slab, just above the slab, and a bit above the height of the sink. Monitor them and see which ones get wet and how wet.
As for no longer being able to duplicate the leak, that is another problem.
Did you jog the pipe when you opened the wall? Had you been using another drain or toilet when you saw the other leaks?
Old 01-18-06, 09:56 AM
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Could the leak be coming from the water supply side around the valve? Try turing on the water, letting it run and crawl under the sink to watch for leaks near the valve.

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