slab leak repair - near old foundation repair with piers

[carrotguy]

Hi,

I posted with some questions a few years back, and I'm ready to follow up. We have an audible hot water slab leak in the Dallas, TX area. It stops when we shut off the hot water valve at the water heater. When we turn the hot water back on, it doesn't start right away. It only starts when we try to run the hot water. I think it's a siphon effect.

I thought about calling a leak detection service, but we can hear the leak pretty well on one side of the wall. My dad thinks the slab is 4" thick at the leak. Can we use a demolition hammer, or do we need to use a jack hammer? We can use a reciprocating saw to cut through any rebar, right?

The property is on soil that's really moist. We're at the end of the block, and the storm drain is in front of our house. I think there might be a leak in the storm drain system that keeps our lawn saturated - there are shallow pits in both the front and back yard. We can use plywood to keep the soil in place when we open the slab, right? Any other tips?

What's the longest length of time we can keep the slab open? If I had my way, the soil wouldn't shift at all.

Thanks.

[carrotguy]

Just for some pitchers, to borrow a term from johnbridge, here is an update. We bought a $80 1" SDS rotary hammer from harbor freight. I would have rather bought american-made, but you gotta choose your battles. The drill and chisel worked well enough, but if you need to clear some area, a demolition hammer would be the way to go. This is a small bathroom, and I'd rather not use a jackhammer unless I had to. If you'll check the map below, we're working in the master bathroom right beside the toilet drain. Note how the water heater is towards the front of the house.

I debated with my Dad to do the tear out in the front bathroom, but there's a cabinet above the problem area and he didn't want to tear it out. It looks like we'll tear it out anyways, since we'll only be able to see the elbow of the hot water supply joint, no matter how deep we go. They didn't suspend the rebar when they poured the slab - the rebar lies at the bottom of the concrete. I'm going to drill into the slab horizontally and epoxy some rebar when we patch it up. We needed a hole in the master bathroom anyways, since the toilet drain has a 1.5" hole in it.

There's a lot of gravel in the leak area. Here are a few questions now....

1) Soft copper is used under slabs if I understand correctly. Since the leak is on the hot water line, there's a joint where it goes below the soil, correct? I've heard not to solder soft copper, so I assume I'll have it brazed. Since there's so much gravel, we'll try to be careful about knocking the pipe around. Is it easy to estimate the extent of a leak with compressed air? Should we only hope that there's a leak at the joint, and not pinholes through the length of the run?

2) I'm gonna check half price books for slab repair/foundation repair texts. Any tips for backfilling? Maybe some terms or manufacturer's to google search? I read a blurb about engineered backfill from a concrete supplier, so I suppose I could stop by one in Dallas. There was a stringy black material in the area of the pipes. Is this oakum? I'm still surprised at the amount of gravel.

[jadnashua]

I wouldn't want any stone near my water pipe...I'd want to surround it with sand, but then, I'm not a pro at this. I'd think that expansion/contraction as you ran hot water, then it cooled off would give you all sorts of grief. Personally, I'd have abandoned that line and run new either through a wall or the ceiling. Fix one leak, and you may find another next year. Not fun tearing up your foundation.

[carrotguy]

I wouldn't want any stone near my water pipe...I'd want to surround it with sand, but then, I'm not a pro at this. I'd think that expansion/contraction as you ran hot water, then it cooled off would give you all sorts of grief. Personally, I'd have abandoned that line and run new either through a wall or the ceiling. Fix one leak, and you may find another next year. Not fun tearing up your foundation.

The attic doesn't have much room in this house. There are a few roof leaks and the power fades out of half the house in bad storms. I'm gonna have to take down the ceiling in some of the rooms to get access to the attic. There's no problem though, cuz there are a few damp spots that need replacing anyways. In any case, there are a few drain problems.... If I'm opening the slab to fix a few drains, this supply line leak shouldn't be too much of a stretch.

How far down do these copper supply lines go into the soil? Is it hard copper brazed onto soft copper? I'll keep the gravel away, but if anyone can suggest any texts that might help, I'm more than willing to check amazon or the library.

Thanks.

[Lightwave]

Personally, I'd worry about the structural soundness of that foundation long before I consider fixing the plumbing. Drywall cracks, evidence of prior repairs, and persistent high water levels all point towards foundation damage. Have a structural engineer look at your foundation first before considering plumbing fixes.

Get something done about that leaking storm drain if at all possible.