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I am trying to fit a 2in shower p-trap between floors with 2x10 joists. Unfortunately, I have a run of EMT electrical conduit directly (about 8in) below the drain; and, as a result, a standard trap doesn't fit right. The best thing I have thought of to work with this is to add a short horizontal run between the drain and the trap (see the picture). I am hoping to take advantage of the Illinois Plumbing Code (*) clause that reads "[a]ll directly connected plumbing fixtures... shall be separately trapped by a water seal trap placed as close to the fixture outlet as possible". (So this is "as close as possible" as I see it!)

So the question is, will this horizontal arm between fixture outlet and trap satisfy the code?

(*) I do not believe the Illinois Plumbing Code differs materially from the Int'l PC in this respect.

p-trap with horizontal arm before fixture

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A lot of double sinks share a P-Trap which constitute offsets.

My only concern would be it looks like you are going to glue all the joints. I would use some slip/joint/nut/gasket connectors so you could take it apart if it clogs.

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  • i had planned to seal it up in my floor for eternity -- replace OSB, cement board, tile -- the works! I guess it would be a pain to auger through the drain, and I suppose that's your point. But except for the arm I may add, is it unusual to seal the thing up like I plan?
    – Drew
    Commented Jun 28, 2023 at 15:19
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    What I mean is, I don't think it's unusual to seal a shower trap into a floor where it couldn't be disassembled even if there were such "slip/joint/nut connectors" -- is that correct? (New at this, so forgive a noob question!)
    – Drew
    Commented Jun 28, 2023 at 15:34
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    You're right that shower traps are often inaccessible, but they're also mandated to be 2" pipe so they can be effectively augured (and are less likely to clog in the first place).
    – isherwood
    Commented Jun 28, 2023 at 15:47
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    The only place I'll use a glue-together trap is a 2" or greater where I have to break concrete to get to it. If the trap can be accessed from a ceiling below, go right ahead and put an access panel there now, and use a screw-together type of trap. Or not, your call. I don't consider even the concrete encased ones to be completely inaccessible, but if I need to go in there and access it, cutting out the pipe is a minor part of the overall pain. Anywhere that's reasonable to access, I'm going to kick myself later if I made the job harder.
    – Ecnerwal
    Commented Jun 28, 2023 at 18:10
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    Thanks for all the comments! For the record, @Ecnerwal, I agree, but these things come down to choices, lesser of evils, etc. In my case, it's a choice between an access panel in the ceiling of my entrance foyer; or a commitment -- if it comes down to it, maybe, someday when it's completely clogged -- to take out a toilet and some annoying-but-repairable drywall and framing and open the hole in the floor again, I'm going to take my chances. Reasonable people might do otherwise! :-) Thanks again, really, for helping me think through this, guys!
    – Drew
    Commented Jun 28, 2023 at 23:09

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