I have a house on a slab that had a bathtub drain that had become
disconnected for some reason, then the bathtub for 'x' years drained
into the ground under the slab, which of course caused the slab to
crack and subside. I got the slab mudjacked, which is marginally
helpful. Slab has wire mesh on the bottom, no rebar inside it.

I thought the route I would have to take would be to have the pipe
replaced leading from the bathtub drain to the main stack, which is
about 6' away. In order to make sure that I knew where said pipe went,
I rented a hammer drill and blew a hole in the slab about 8-9" across,
right where the pipe should have been. Of course, it wasn't there.
Then to prove my theory, I went over by the stack and dug another hole,
and of course the bathtub pipe doesn't connect there at all.
Apparently it connects more or less where the waste pipe leaves the
house.

So in order to - as one replier suggested a few days ago - get at the
drain under the tub, I made a third hole in the concrete slab, just to
be able to get in there and work. I dug out the dirt and mudjack cr*p,
and connected the tub to the original drain (which is an "S") and
voila, the darn thing works like a charm. I just let the water run in
the tub for half an hour, and there's no spills.

So but now I have three concrete holes. I think what I should do is
fill them with sand, compress it as best I can, then mix up some
industrial-strength concrete in a bucket and fill the holes. Does this
make sense ?

If nothing else I hope you enjoy the story about someone who was so
sure their theory was correct !

wrote:
I have a house on a slab that had a bathtub drain that had become
disconnected for some reason, then the bathtub for 'x' years drained
into the ground under the slab, which of course caused the slab to
crack and subside. I got the slab mudjacked, which is marginally
helpful. Slab has wire mesh on the bottom, no rebar inside it.

I thought the route I would have to take would be to have the pipe
replaced leading from the bathtub drain to the main stack, which is
about 6' away. In order to make sure that I knew where said pipe went,
I rented a hammer drill and blew a hole in the slab about 8-9" across,
right where the pipe should have been. Of course, it wasn't there.
Then to prove my theory, I went over by the stack and dug another hole,
and of course the bathtub pipe doesn't connect there at all.
Apparently it connects more or less where the waste pipe leaves the
house.

So in order to - as one replier suggested a few days ago - get at the
drain under the tub, I made a third hole in the concrete slab, just to
be able to get in there and work. I dug out the dirt and mudjack cr*p,
and connected the tub to the original drain (which is an "S") and
voila, the darn thing works like a charm. I just let the water run in
the tub for half an hour, and there's no spills.

So but now I have three concrete holes. I think what I should do is
fill them with sand, compress it as best I can, then mix up some
industrial-strength concrete in a bucket and fill the holes. Does this
make sense ?

If nothing else I hope you enjoy the story about someone who was so
sure their theory was correct !

I'd let the holes dry out somewhat, backfill with sand (you can use
soil but sand will compact easier than wet soil) to the level of the
bottom of the sab. Fill in the missing concrete with RapidSet &(~$15 /
bag 60lbs .44 cubic ft) you're done.

Just about everything in remodel / repair / retrofit differs from the
original plan. The key is to be able to adjust & correct on the fly.

All that matters is that it is safe, it works, doesn't create more
problems downstream & looks good.

Glad it worked out & you didn't have move that tub.

I'd say it could classified as a very successful repair job.

cheers
Bob

Thanks for the reply ! I am thrilled that the old drain works, that
saves me quite a bit of expense.