Offset p-trap OK?

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Stereo

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I have a couple of obstructions I need to work around to connect a new shower to the horizontal drain line so I need to offset the P-trap. The shower is a guest shower and will only rarely be used so I don't anticipate issues with a buildup of odor due to accumulation of debris and I'll make sure the p-trap doesn't run dry.

Is the layout pictured below OK? I can't go under the duct because I don't have enough height to connect to the horizontal drain line. Per the 2018 IPC, the depth of the drop to the weir is under 24" and the distance from the center line of the shower inlet to the P-trap inlet is under 30".

NOTE: This is just a dry run. In the photo, it looks like the horizontal drain is going uphill. I'll make sure there is proper slope when gluing up.

Thanks for your advice!
Offset trap.jpg
 

Stereo

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Why can't you move the trap to the right and use a single horizontal segment after the trap?

Cheers, Wayne
Oops. I should have been more careful with my drawing. I was mainly focused on the plumbing configuration. I have attached a more accurate depiction showing the joist level and change of direction.
Offset trap_corrected.jpg
 

wwhitney

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Same question still applies, why not extend the segment that's at a 45 from the shower tailpiece, then when you get to appropriate height, put a 45 on to turn down straight into the trap?

That would certainly be fine.

Cheers, Wayne
 

Stereo

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Same question still applies, why not extend the segment that's at a 45 from the shower tailpiece, then when you get to appropriate height, put a 45 on to turn down straight into the trap?

That would certainly be fine.

Cheers, Wayne
Bad drawing again. The duct doesn't allow the 45 to continue down. The duct interferes by about a half inch. There's no budging the duct. All joints are locked in with "solid" duct seal.

The plumbing I have laid out IS the only way I can get the run to fit. Please let me know if there are any code issues with what I have shown. Thanks!
 

wwhitney

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Assuming you've gotten the applicable distance correct from the IPC, then it meets the IPC. But still probably a bad idea. How about a pair of 60 degree bends to get to the trap, so that there's no section upstream of the trap that's only at 2% slope?

Cheers, Wayne
 

Stereo

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How about a pair of 60 degree bends to get to the trap
I thought the drain pipe/tail piece had to fall vertically. Am I wrong? As I understand the code, only deviations up to 45 degrees is considered vertical. I can shorten the horizontal section upstream of the trap to only an inch or so. Thanks for your feedback!
 
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Stereo

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I think the section before the trap may smell.
I did read that could be a concern, but only from a buildup of debris, which as I noted in my OP, may not be a concern. I will keep runs as short as possible to the trap to make cleaning of the pipe easier.
 

wwhitney

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I thought the drain pipe/tail piece had to fall vertically. Am I wrong?

Well, if that is/were true, then your proposal would not be OK, as you have a horizontal section upstream of the trap. And the IPC wouldn't specify a maximum 24" vertical and 30" horizontal between the fixture outlet and the trap--you couldn't get more than 24" horizontal with only 24" vertical.

Anyway, there's noting like that in the IPC:


My thinking was that a consistent 30 degrees above horizontal would be better than a 45 degree segment followed by a horizontal segment. But that's mostly a guess.

Cheers, Wayne
 
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