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Thread: Water leaking under slab

  1. #1
    Join Date
    Nov 2021
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    Central Arkansas
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    Unhappy Water leaking under slab

    My wife was walking in the kitchen barefoot and noticed around one wall the tile was warm. Then she went into the adjoining bathroom and the tile in there was also warm, both in an area about 3 feet square. Water and light bills were only $10~$15 more than last month. The house was built in 1978 with copper plumbing throughout. I'm thinking we have. a small leak in the hot water line feeding the bathroom. I've called a foundation repair company (Olshan's) and they're coming on June 1st to check it out.
    Was wondering if any of y'all have had a similar problem and what it took to fix it. Not looking forward to jack hammering the floor in the house, but don't know of other options. There are 90* elbows on some of the exposed piping I've seen in the house, so I don't think sleeving is possible.
    TIA,
    BillL

  2. #2
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    Depends on the volume of water and the soil underneath. I am on a less than ideal lot, and have probably close to 3k gallons of water under the slab of my garage floor since Nov 2021. Is my garage slab likely to "settle" a little more this summer, yes. Is my boiler guy going to show up muy pronto when I have all the parts I need, "hope so."

    The wife and I use, before the leak started, 50-60 gallons per day average between the both of us. We are well up over 100 gallons per day average since November. We were confounded by having both daughters (with long hair each) home for Xmas. We got the water company involved and those guys went bananas. There were two of them in the truck. The first one came in ( I took the afternoon off to meet them), with a very bright flashlight and was the confused. He asked if he could 'phone a friend,' I said yes and the older guy waiting in the truck came in with a flash light and he ended up confused too.

    Eventually we figured out the wet spot on my garage floor under the water heater = 50 gallons per day. I just dropped $3500 (Friday) on a new boiler, with another $600 in the next couple days (when the rain stops) to bring home a new water heater too. Once I am done chiclet-ing the garage, another $5k to our boiler guy to install the new stuff. I am using a special loop on the boiler to make hot water, for me the 'hot water heater' is just a storage tank for hot water.

    FWIW my sister in central California is 'repiping' this summer. She is in a +/- 1975 build and gets to replace all the copper piping this summer. We are scheduled to have margueritas together in September. The trouble with that is my B-i-L is partial to Scot's whisky. Tequila + scotch is not a marriage made in heaven.

  3. #3
    William,

    Call a reputable water leak detection company. Oshan won't be able to tell you much about the water leak. Also, you may very well have slab access coverage on your home owner's policy. Give your agent a call tomorrow as well. I am a property insurance claims supervisor dealing primarily with Texas policies. We see slab leaks on a regular basis. The plumber might be able to do you a hot water line reroute pretty reasonable much better than having your slab cracked up.

    Jack

  4. #4
    If you have a water meter, with everything turned off, read the meter. Wait one hour and read it again. Reading should be the same. If it isn't, turn off supply line to water heater and repeat the test. Then if reading doesn't change, then you have a leak in hot water line under slab. Never understand why most leaks are in the hot water side rather than cold side of supply lines. Holder of a P-1 Plumbing Licensee in a previous lifetime.

  5. #5
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    Ok, maybe I've lived in SoCal too long, but I'm having problems visualizing why there would be hot water lines under a slab foundation in the first place. Why would any water line need to be under a slab inside the house perimeter? Drain lines, yes, but water lines?
    (And yes, I've lived in places where pipes can freeze, I've lived in places with slab foundations, but not both at the same time.)
    Yoga class makes me feel like a total stud, mostly because I'm about as flexible as a 2x4.
    "Design"? Possibly. "Intelligent"? Sure doesn't look like it from this angle.
    We used to be hunter gatherers. Now we're shopper borrowers.
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  6. #6
    Under the slab runs can't have any joints beneath the slab.

  7. #7
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    Quote Originally Posted by Lee DeRaud View Post
    Ok, maybe I've lived in SoCal too long, but I'm having problems visualizing why there would be hot water lines under a slab foundation in the first place. Why would any water line need to be under a slab inside the house perimeter? Drain lines, yes, but water lines?
    (And yes, I've lived in places where pipes can freeze, I've lived in places with slab foundations, but not both at the same time.)
    It’s very common in ranches-on-slabs, at least in the Midwest, as attic space is typically unconditioned, so water lines can’t go there due to freezing, and horizontal runs of water lines through walls is asking for trouble, too.
    Jason

    "Don't get stuck on stupid." --Lt. Gen. Russel Honore


  8. #8
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    Quote Originally Posted by Lee DeRaud View Post
    Ok, maybe I've lived in SoCal too long, but I'm having problems visualizing why there would be hot water lines under a slab foundation in the first place. Why would any water line need to be under a slab inside the house perimeter? Drain lines, yes, but water lines?
    (And yes, I've lived in places where pipes can freeze, I've lived in places with slab foundations, but not both at the same time.)
    I suspect it is a case of need versus ease. North Carolina experience here, decades ago. Headed to site #142 to put in drains? Great. If you can get the supply lines with vertical stubs in before the gravel truck shows up ahead of the slab pour you have saved time, and time is money. Compared to drilling all the studs and soldering all the corners, running supply lines under slab is fast - but might not meet SoCal earthquake code. Sucks to repair later, but the builder is making money. M2c.

  9. #9
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    Quote Originally Posted by Jason Roehl View Post
    Itís very common in ranches-on-slabs, at least in the Midwest, as attic space is typically unconditioned, so water lines canít go there due to freezing, and horizontal runs of water lines through walls is asking for trouble, too.
    Quote Originally Posted by Scott Winners View Post
    I suspect it is a case of need versus ease. North Carolina experience here, decades ago. Headed to site #142 to put in drains? Great. If you can get the supply lines with vertical stubs in before the gravel truck shows up ahead of the slab pour you have saved time, and time is money. Compared to drilling all the studs and soldering all the corners, running supply lines under slab is fast - but might not meet SoCal earthquake code. Sucks to repair later, but the builder is making money. M2c.
    Sounds like both cases involve climates that get freezing air temps but not deep frostlines...come to think of it, my living places have tended to one extreme or the other.

    I can (almost) see the frozen-attic reasoning, although it seems like there are easier ways to skin that particular cat. The phrases "drilling all the studs" and "horizontal runs through walls" both trigger my SoCal sensibilities: that mostly crops up in short runs because a fixture is under a window or the ceiling joists run the wrong way in a two-story. Everything else here tends to be up-and-over from stud bay to attic to stud bay.
    Yoga class makes me feel like a total stud, mostly because I'm about as flexible as a 2x4.
    "Design"? Possibly. "Intelligent"? Sure doesn't look like it from this angle.
    We used to be hunter gatherers. Now we're shopper borrowers.
    The three most important words in the English language: "Front Towards Enemy".
    The world makes a lot more sense when you remember that Butthead was the smart one.
    You can never be too rich, too thin, or have too much ammo.

  10. #10
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    If you have an "island" in a kitchen with a sink, the lines will be run under the slab. Otherwise you'd see a "drop" from the attic. So that is one reason to run lines under the slab.

  11. #11
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    Feb 2006
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    DFW, TX
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    My house was built in 1973 and I've had 2 slab leaks, about 10 yrs apart, both of them hot water going to our kitchen about 50 feet away from the hot water heater. I was told by the plumbers that it was primarily due to the shifting clay soil that we have here in N Texas.
    With the first, they dug up and fixed it. They missed it the first hole and had to dig a second. I found out how poorly they repaired the floor a couple of months ago when I replaced some carpet with vinyl flooring.
    On the second leak, the plumber suggested running a pex line into the attic and back down. This saved a lot of time and mess and several hundred dollars in the process.
    Insurance paid for both, but I feel a lot more confident that I won't have any further issues.
    It's never too late to have a happy childhood.

  12. #12
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    Quote Originally Posted by Brice Rogers View Post
    If you have an "island" in a kitchen with a sink, the lines will be run under the slab. Otherwise you'd see a "drop" from the attic. So that is one reason to run lines under the slab.
    I'd blanked that instance out of my mind.

    A friend had her kitchen remodeled a few years back, and insisted on that "feature. It was not a pretty process, and added about 10% to the total cost, all to have a small bar-sized sink six feet away from a larger one. (I'll admit that tying the drain line into the existing one was more of a deal than the feed lines.)
    Yoga class makes me feel like a total stud, mostly because I'm about as flexible as a 2x4.
    "Design"? Possibly. "Intelligent"? Sure doesn't look like it from this angle.
    We used to be hunter gatherers. Now we're shopper borrowers.
    The three most important words in the English language: "Front Towards Enemy".
    The world makes a lot more sense when you remember that Butthead was the smart one.
    You can never be too rich, too thin, or have too much ammo.

  13. #13
    Join Date
    Mar 2019
    Location
    Los Angeles, California
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    572
    When I was a carpenter building homes, we sleeved all copper runs under slabs with a plastic foam sleeve, about a quarter inch thick. Something about the acidity in the soil causing pin prick holes in the copper. We used schedule 80 copper pipe under slabs which is about double the thickness. Indeed in all exterior buried applications schedule 80 was typical.
    Regards,

    Tom

  14. #14
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    SE PA - Central Bucks County
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    This reminds me of the many thousands of homes in the two Levittown PA (and likely the same in Levittown NY) that were all on slabs with both radiant heat (no PEX back then) and in-slab water runs. Conversions after they failed over the years became an art form. Replacing the heating was a lot easier than the water supply stuff for sure but a lot of pipe got laid in the attic as a result or through jackhammered channels in the slabs.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  15. #15
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    Nov 2021
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    Central Arkansas
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    We found another company to check out the problem. Had a van full of sophisticated looking equipment that they used to trace where the water line was routed from the tank to all the outlets in the house. Then they shut off the water and connected an air line to the washer hot water faucet and walked down the route of the hot water line with an electronic stethoscope device to find the exact position of the leak.
    The good news is that the leak is between the water heater and the first junction. They will cut the line at the heater and the front bath lavatory and run a new PEX line through the attic. The bad news is that this may be the beginning of an ongoing problem. This blows my lumber and travel budget for this summer. :-(
    BIllL

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