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Paul Wharton
hot water leaking under a slab

I have a 17 year old ranch slabber with a hot water leak under the slab. I conducted a test: the valve from the meter to the house service open; a separate valve to the hot water open; no faucets in the house open and the water meter still moves. The valve from the meter open; the valve to the hot water service closed; no faucets open and there was no movement on the water meter. I concluded that there must be a leak somewhere in the hot water lines embedded in the slab, but (thankfully) not the cold water lines. I have no evident damp spots anywhere in the house so I think it must be leaking under the slab. Right now we are dealing with the problem by leaving the hot water service to the house off until hot water is required for showers, clothes washer or dishwasher.

I have been told by a couple of plumbers I have contacted that there are 2 avenues of repair I can pursue:

1. Locate the leak (which could be problematic since there is no apparent evidence of a leak), chip the concrete from around the leak to expose the copper and repair the existing pipe, then patch the slab. This on the face seems the route to go, but what if I fix one leak, and it turns out that it was not the only one? Is there any way to determine before hand if more than one leak exists? Also, what if the leak happens to be right under a load bearing wall? Will that complicate things?

2. The other solution I was given is to replace the existing hot water service by fishing new pex-tubing through the attic to all of the existing hot water outlets and sealing the current hot water pipes in the slab. I have some concerns about this however. I'm not sure I like the idea of having water service through the attic because of possible freezing and rupturing the pex and in the long run the additional cost to repair the damage. Another concern I have is will this method raise any flags with a home inspector if I decide to sell the house in the future or will this method affect the value of the home?

I know that without more information it would be hard to predict, but as far as expense is concerned does anybody have a clue as to which might be least expensive?

HELP!!! I'm really beyond the knowledge that I have in dealing with this problem and can use any advice that I can get. thanks!

Re: hot water leaking under a slab

There are leak detection company's that can pinpoint the location of the leak. We deal with it quite often in Florida. What we advise our customers to do is locate and repair the first leak. When a 2nd one appears (which could be some time) then consider a re-pipe. But not just the hot, do the cold at the same time. If you don't turn the water off at the heater you may be able to find a hot spot in the slab near the leak.


Re: hot water leaking under a slab

I assume that your pipes are copper. John advice is solid.

But if it were me, and believe me, I've been there done that, I'd re-pipe now.

Why? it's at least $250 to locate the leak, it's at least $400 to have it repaired unsuccessfully. Yes, unsuccessfully. You'll spend at least $650 before saying: "I should have repiped".

BTW, the likelyhood of getting a second leak very quickly is high.

Re: hot water leaking under a slab

What they said, especially the part about the second leak. Which you may have already. When scoping the pipes, don't stop at the first leak. Check all the pipes.

Re: hot water leaking under a slab

I have never used it but I have been on large restoration jobs that used an Epoxy pipe lining company to restore drinking water and other types of pipes that were not accessible with out major removal of other materials.

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