Hello, first post here. I have a question regarding shower drains and whether it meets code. In this situation I'm re-doing the shower drains because the traps were freezing. There are two showers upstairs (right next to each other) that drained into the same stack with 2" copper drain plumbing. The far shower is in an overhang of the building, so cold outside air is below the shower. Despite insulation, the copper P-trap freezes in the winter. My solution is to move the P-trap into the lower building wall (in line with the close shower), so it's more protected, and replace the copper with ABS at the same time. This required re-doing the P-trap of the close shower too. I have no doubt this will function well. But I'm curious if it meets code (general UPC code, ignore specifics that may be in place in my jurisdiction).

Below is a photo of the new plumbing, with the P-traps both draining into a 2" arm that goes back to the stack.
There's a 4-foot arm of 2" ABS now (not shown in the photo) from the far shower to the new P-trap. The close shower's new P-trap is right below the shower, mostly obscured from view in the photo, but you can see the outlet of the P-trap in the back.

My main concern is the 45 deg. drop from the outlet of each trap to the double sanitary tee. The lower elevation after the drop is still above the bottom of the P-trap. The 1-1/2" pipe coming out of the top of the sanitary tee goes to the vent. I couldn't figure out a better way to do it in this situation... Any thoughts?

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It looks like you have managed to create TWO "illegal 3/4 'S' traps".

Your double ty cant be below the outlet of the trap and your vent cant offset horizontally until you are 6 inches above the highest flood rim level on the floor. You can use 45s to offset below the flood rim level and your 90 below the cross need s to be a long sweep or a wye and 45 with end clean out. In some states you can t use a double ty on a vertical and it has to be a double fixture fitting or a double wye.



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why are the traps on the other side of the pink wall?
put the double san tee where it is. come out of each side with short nipples and put the trap there. offset from the trap inlets up to the shower drain.
the vent should be OK because you have no other choice,
the traps need to be the type with the cleanout plug on the bottom.

Okay. I guess, to really do it right, and avoid the horizontal offset of the vent (since I can't go straight up there), I should do away with that vent altogether. The shower drains should each come out of the pink wall with 45's downward, then each go to their own trap that outlets at the level of the arm that goes to the stack, and come together in a horizontal 3-way wye (double wye) with a cleanout in line with the arm to the stack. The stack will then act as the vent (as it did with the old copper configuration), which is less than 5 feet away from the traps, and there will be only 1/4" per foot drop between the trap outlets and the stack. Sound good?

Thanks so much!



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Not with two traps joining the line before the vent.

Not with two traps joining the line before the vent... Hmm.

How can I do this then? If I'm forced to choose the lesser of evils, is a horizontal offset vent below flood line better than two traps joining the line before the vent?

Or joining the lines BEFORE the trap (having one trap for both showers)... I'm guessing that's even worse, right?



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I would cut a little more sheetrock out and make a horizontal turn back into the wall with the main drain. Once you get back in the wall, turn up to the vent and use a back to back fixture fitting to catch both traps.

What do you mean by "turn up to the vent"? The vent on the main drain is a 4" galvanized stack, which goes up through the upstairs floor with very little clearance, not easy to tie into... is that what you were suggesting?

I was referring to the 1 1/2" ABS coming out the top of that double tee. Doesn't it turn vertical pretty soon ?

Unfortunately not. It goes back horizontally 4 feet to the old copper stub where the outside shower drain previously connected, and the original vent pipe goes up from there. So that's probably a bad thing. I'm now thinking about how to attach a new vertical vent to the stack above where the drain arm comes in, but it'll be tough.

That would be a definite No/No. You do not want one drain flowing past another one before the liquid reaches the vent.