The background is that I am putting a full bathroom in my basement. My builder stubbed out dwv lines for all three fixtures under the slab. I have since cut open the slab, removed gravel to expose the stubs and make room to install drain lines.

I also cut a trench diagonally across the floor to run the line for a floor drain I put in a closet for the water heater. This trench terminates in the slab cutout for the shower drain.

I did not put a trap on the floor drain because it will be used so infrequently that it will dry out. What I was planning on doing was tying the floor drain line into the riser of the shower drain above the p-trap. That way a single p-trap would seal both lines. All these lines are 2" PVC.

I am at the point where I have dry fit all the lines, except connecting to the stub. I am still slightly intimidated by how bad it will smell.

My concern is that my dwv tee is too low on the shower riser and will allow waste from the shower drain to come part way up the floor drain line before it exits through the p-trap. Now, I am in no way worried that it will actually come all the way up and out the floor drain, there is too much slope for that to happen unless there is a clog. I tried to illustrate the situation below. The distance between the bottom of the floor drain line and the top of the p-trap is 1 1/4". Should I be concerned with this setup?


Shower drain
|
Floor drain line ________|
| |-------- Exit to septic tank
\__/
p-trap

My picture did not post correctly, but if you quote my original post, you can it will appear correctly in your reply.

Most floor drains have a built in trap and you would be double trapping the flooe drain and that's illegal. A much better idea would be to connect the floor drain to the house main and fill the trap with cooking oil or antifreeze. Good luck, tom

Speedball1,
Thanks for the quick reply. I cut the slab and installed the floor drain line myself, so I know there is no trap. I simply put a sweep 90 on the end with a short riser to the drain cap.

Like I said in my original post, I am dry fitting all the lines now, so now is the time for me to make any adjustments.

Now, if I understand correctly, you are recommending that I install a p-trap at the floor drain and then connect to the main drain line rather than connecting to the riser above the shower trap. That sounds feasible because the floor drain line comes into the 30"x30" cut out in the slab I made for the shower.

That leaves me with two questions. Can I install the p-trap for the floor drain 6 feet downstream from the actual drain in the floor, in the slab cutout for the shower, or should I put it diretly below the floor drain? The reason I ask is because there is some rebar I will have to cut to install the trap below the drain.

Second question, can I use a 2"x2"x3" wye fitting to connect the exit lines of the shower p-trap and floor drain p-trap together as they go into the main 3" drain line?

Thanks,
Eric

btw- how long will cooking oil/antifreeze last in a trap?

Hey Eric,
This is a typical floor drain. Does yours look like this? (see image) Tom

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Speedball1,
No, what I am calling a floor drain is only the part that is visible at the surface of the floor. It is glue on PVC part. I circled what I have in your picture. There is no trap below.

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