Leak inside slab - just abandon lines and reroute?


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Old 03-07-16, 08:50 PM
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Leak inside slab - just abandon lines and reroute?

Ugh. So, have a potential PITA plumbing issue.
Late 60s ranch. Our laundry room and far bathroom are on a 4" raised cement slab that is on the back end of the garage slab, connected to the side of the house.
Somewhere inside this slab, there is a water leak I can't get to. All I know is that there are water lines I can see from the basement that go through the rim joist into the slab. There is laundry and a toilet on the exterior wall, and a sink on an opposite interior wall but the supplies to it come up from the floor, not in the wall.
So, at some point in the floor they must split to serve the two places. All I know is that somewhere embedded in there the cold line is leaking. We didn't even know, I just noticed one day last fall that I could just barely hear water flowing, and if I jiggle the supply line to the sink it changes pitch... and the well pump was running a lot. Otherwise no signs of water. As far as I can tell water was just leaking under the slab. So, we just cut off the water unless we do laundry until I can fix it
Well now water has started appearing in the adjoining basement wall floor seem, so it's time to do something about this...

I assume the *right* way to fix this is to bust up the darn slab, but I don't even know where the leak is. What a pain.
But I wonder - is there any reason I couldn't just cut off and abandon the existing lines, and instead re-route new ones to the fixtures? That will be a pain too, b/c I'll have to go from a source in the basement all the way up into the attic and across, then down into an exterior wall. But even that seems like less work. I don't like that option either b/c it means having to fix the lines up through a wall, a lot of added length, and routing across all the insulation etc up there.
 
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Old 03-08-16, 05:24 AM
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Option 1 is to cut the concrete and bust out slots to run new pipes. Option 2 is to reroute the pipes some other way. Most commonly it's done up and through the attic.

If rerouting the pipes, because of your location, I would use PEX and have no joints in your attic. The pipe is available in long coils and I would make sure you have a continuous pipe with no pipes or fittings in the attic or outside walls. You should get the piping as close to the heated space of the house and insulate over them very well to limit the chance of freezing but should they freeze PEX pipe can withstand it without damage.
 
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Old 03-08-16, 06:55 AM
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Could you bring it from basement to outside and bury it to the points where you need it?
 
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Old 03-08-16, 07:59 AM
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I assume the *right* way to fix this is to bust up the darn slab
I would say the right way is your other idea. Bypassing the slab is done all the time here due to slab leaks. It's very expensive done by professionals.

Your situation is a little easier than most slabs, you know where the water enters the slab.
 
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Old 03-08-16, 08:10 AM
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Fortunately (well, not really) since the house is form the 60s, the attic insulation sucks and it's not that cold up there. Originally just R13... I added a layer of R30... I could run it between or under those bats.

Here's the rub w/ PEX and "no joinsts" though - I need to supply both the laundry, which is on the exterior wall, AND a sink in the bathroom that is past it and would go down an interior wall.
So I'm not sure how I can avoid a T in the attic?
Unless I did something crazy like run 4 (2x h & c) lines up, then down to the laundry, and put the T there so it then goes back UP and over again to the sink?
That still puts a joint in the wall, but it happens to be an area where there is already an access panel to the joist space.
 
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Old 03-08-16, 04:13 PM
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I would just do your best to get the piping and especially the fitting as close to the heated part of the house with lots of insulation on top. The brass PEX fittings are quite good. I let my unoccupied rental houses freeze and I don't drain the piping and I've never had a fitting or PEX tubing fail.
 
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Old 03-08-16, 07:12 PM
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Testing companies will set you back $350 to $400 to find the exact leak location. I have done this and the testing company was spot on exactly where the leak was. I busted up the slab, repaired the leak with a configuration that would allow future expansion and contraction without fail and then sealed up everything. Much cheaper than rerouting plumbing. The kicker, is that there is no guaranty that there will not be another leak somewhere else down the road.
 
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Old 03-09-16, 09:05 AM
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"The kicker, is that there is no guaranty that there will not be another leak somewhere else down the road."

That to me is the best reason to NOT repair it, but instead bypass and run all new lines...
 
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Old 03-09-16, 11:37 AM
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In some areas of my county well water is pretty corrosive to copper. I had a couple rental houses with copper pipes buried in the slab. Once there was one leak it was only the tip of the iceberg. Bypassing the slab and running all new lines was the best long term solution. One house I went up and through the attic. In the other I trenched around the outside and ran the lines around the exterior perimeter underground. They are options but I can't say either is particularly easy.
 
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Old 03-09-16, 12:09 PM
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That is a really good point.
We have this problem - water is acidic. All of the original copper piping has been replaced over the years due to leaks... lots of little green stains on the basement floor.
I'm sure what's in there is copper and it probably was just time.

Hm that kind of seals the deal to me b/c short of cutting out a large chunk of the slab, I couldn't replace it all.

Someone on another forum suggested doing a "home run" approach w/ PEX and a manifold in the basement, that way I could avoid junctions in the attic. Just means fishing 4 pipes instead of 2.
 
 

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