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We are gutting and rebuilding our basement, and part of that included removing an improperly installed shower and replacing it with a bathtub. However, in order to position the tub so it fits in the room, I need to move where the drain down-tube is. Below is the current setup:

enter image description here

Ideally the down-tube should be located in the upper right corner, right about where the pipe comes out of the foundation. The horizontal drain is below or within the concrete of the basement floor, so I can't really position anything there. I bought a ton of different angle pieces and some pipe to see if I could arrange something to get it near the desired location. But as soon as I started, I realized one piece that could fix it directly... if it's allowed. I have the P-trap I was planning to install on the repair, and it is the kind with a screw on attachment to the horizontal drain. If I swivel that all the way around, it will fit directly with no additional pieces needed. See the pic below for roughly what I would like to do:

enter image description here

So my question is if this is legal (code) and will it work? It seems like it should be, since it's a legal P-trap, but it's turned in a way that it looks like a loop. I feel like this isn't any different than having the trap in the same plane as the horizontal vent, but the loopy bit has me worried. Anything wrong with this setup?

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  • Mazura pointed out below that you appear to be installing 1-1/2" pipe below concrete. This doesn't meet code in many jurisdictions. Can you confirm?
    – isherwood
    Commented Mar 29 at 12:42
  • I believe the pipe below the concrete is 1-1/2", but that was installed when the house was built in 2000. I'm only attaching to that pipe, not changing the drains or adding more concrete. This is within a box that was set before the concrete was poured to leave access to the drain. I'm planning to leave access from the other side of the wall to get to the P-trap. Also, I'm pretty sure the vertical drain it connects to beneath the concrete is 2".
    – techturtle
    Commented Mar 29 at 18:03
  • Just FYI, this was probably illegal then, too. It likely won't be a problem unless you're scrubbing sheep in your tub, though. PVC is really slippery.
    – isherwood
    Commented Mar 29 at 18:09
  • And for me it'd have to be cast iron, clay, or copper; can't put PVC below grade.
    – Mazura
    Commented Mar 29 at 18:31

1 Answer 1

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A trap can be oriented in any horizontal position as long as the vertical configuration remains standard. Mechanically (hydraulically) there's no difference whatsoever--it's the exact same number of vertical turns (or degrees, radians, whatever). Have at it.

Since you're cutting off the old trap anyway you could install a 45° elbow below the existing coupler to give yourself more clearance. If you happen to have an inside cutter you could remove the coupler and put the elbow on the stub.

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  • 710.2.1 Each horizontal drainage pipe shall be provided with a cleanout at the upstream end of the pipe and in changes of direction over 45° ecodes.biz/ecodes_support/free_resources/Louisiana/Locked_PDFs/… - IDL that it's 1-1/2" pipe about to be encased in concrete with no clean out in the first place, let alone that it goes backwards. Mechanically when I come to rod it, I'm'a be upset.
    – Mazura
    Commented Mar 29 at 2:38
  • You're right on both points, but trap direction doesn't change anything in that regard. You have a 180 and a 90 no matter what. The snake doesn't care which compass direction it's heading in.
    – isherwood
    Commented Mar 29 at 12:43
  • Yep, once the water goes down into the trap, it doesn't matter which horizontal direction it goes after it comes back up out of the trap. As long as the elevation out is lower than the elevation in.
    – Huesmann
    Commented Mar 29 at 17:06
  • I confirmed with one of the county inspectors that this will be a legal setup in my area, even with the 1-1/2" PVC under the concrete (prior build). He did say that the slip fitting (screw on part) was not allowed, because it would be considered inaccessible once the tub was mounted. So I have to change to a glue-in P-trap, but otherwise this size and orientation is legit (at least for me).
    – techturtle
    Commented Apr 1 at 22:33

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