Running drain for new shower under old slab

I want to add a shower to an existing half bath on the first floor of my house. The bath is on a slab and the existing plumbing is run through that slab. I've attached a (badly drawn) floorplan to help show what I'm talking about. The new shower is shown in grey on the floorplan and is going into space that is currently part of the garage. Getting water to the shower won't be an issue, however I'm having trouble figuring out how to drain the shower.

The main floor of the house is about 1 foot (or two cinderblocks) higher than the garage floor, so I'll need to build up the floor under the shower to make it even with the floor in the bathroom. The bathroom is reasonably new with a tile floor that I would like to leave intact. From the garage side, the lower foot of the wall between the bathroom and the garage (the part that is under the house's slab) is cinderblock. I'm wondering if it might be possible to go through that cinderblock wall from the garage and access the toilet's drain from under the slab. Hopefully I could then install a T connection for the shower.

Do you guys think that might be at all feasable? Do you see any other good way to drain this shower?

Thanks much,
Brett

I take it you don't have a basement...do you have any idea which way your drain line exits the house? Does it go out under the garage? Excavating underneath a slab can be done, but it could get dicey. The edge is often thicker than further in, so you'd be trying to work at a very awkward angles.

You have a good situation where you can make that shower a handicapped accessible one since have the depth (i.e., no curb). You may not need it now, but it may be a big thing when it comes time to sell the house, but you need to adhere to certain size issues (well, you could make it curbless regardless, it just wouldn't meet ADA guidelines...still easier to shuffle into rather that stepping over a curb).

For tiling and help in that aspect, check out www.johnbridge.com.

drain

You probably would not, and should not, connect to the toilet's pipe. It will probably be MUCH cheaper and easier, to tear up the floor and replace it afterwards. You will need a lot of space to work on the piping if you were to tunnel underneath. If you can find the right pipe, it may be low enough that you do not have to elevate the shower, which would be a VERY hazardous thing to do unless you made a large platform so you did not have to step out of the shower right onto some steps. Unless this shower is for your wife and you have a large insurance policy on her, in which case we might be watching your story on one of the "They thought they were so smart" crime videos.

hj said:

You probably would not, and should not, connect to the toilet's pipe. It will probably be MUCH cheaper and easier, to tear up the floor and replace it afterwards. You will need a lot of space to work on the piping if you were to tunnel underneath.

Click to expand...

Why shouldn't I connect it to the toilet's drain? I'm not talking about connecting it to the toilet itself, but rather the toilet's drain under the slab. This, of course, is assuming I can actually locate the pipe under the slab and get enough room to actually work on it.

If you can find the right pipe, it may be low enough that you do not have to elevate the shower, which would be a VERY hazardous thing to do

Click to expand...

Actually, the whole point of this is so that I *don't* have to elevate the shower (as compared to the bathroom floor). My layout is a bit difficult to describe, but my existing bathroom is the same as what's shown in the drawing above, but without the shower. The shower is going to be put into a space that is currently part of the garage. The garage floor is about 1 foot lower than the bathroom floor, so I will need to elevate the shower up off of the garage floor, but that's so that it will make the bottom of the shower even with the bathroom floor.

Thanks again,
Brett

jadnashua said:

I take it you don't have a basement

Click to expand...

Correct... no basement

do you have any idea which way your drain line exits the house? Does it go out under the garage?

Click to expand...

Unfortunately, I have no idea... I'm debating removing the toilet and trying to send some sort of a camera down to see if I can see which way the pipe runs.

Excavating underneath a slab can be done, but it could get dicey. The edge is often thicker than further in, so you'd be trying to work at a very awkward angles.

Click to expand...

Yeah, that's kind of what I'm afraid of... I suspect I could manage to take out one or two of the cinderblocks and dig out from under the slab a bit, but I'm a little afraid that after I do all that work that I won't have the space to actually connect to the pipe anyway.

You have a good situation where you can make that shower a handicapped accessible one since have the depth (i.e., no curb). You may not need it now, but it may be a big thing when it comes time to sell the house, but you need to adhere to certain size issues (well, you could make it curbless regardless, it just wouldn't meet ADA guidelines...still easier to shuffle into rather that stepping over a curb).

Click to expand...

That's actually a very interesting idea. Not so much for my wife and I, but one of the reasons we wanted to put this shower in on the main floor of the house is because my wife's grandparents will be staying with us for a while and she wanted to avoid having them go upstairs to where the current bedrooms and full baths are.

Thanks again,
Brett

If you wye into the large 3" or 4" waste line, you will want a vent between the wye and the trap of the shower.

That vent can tie into other vents at 42" above the floor.