Moving shower drain across floor joist

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Positronus

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Below is the diagram of my bathroom plumbing system, hopefully it's somewhat correct. I'd like to move shower drain to the right of the joist (marked with 'new'). I was thinking about following options, that might as well be incorrect because I am not very versed in plumbing codes:

* Move drain pipe through the joist to the right and establishing p-trap there
* Moving current shower wye above the tub wye and establishing p-trap there

plumbing.png.jpg
 

wwhitney

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New Jersey uses the NSPC, which is not so common, so I'm not very familiar with it. My comments:

Your drawing seems to have horizontal dry vents below the floor? That's unusual, and not allowed by the IPC, and with only a limited allowance in the UPC. It looks like the NSPC also has a limited allowance for it, does your DWV comply with that exception?


Also, it looks like the shower is currently wet vented by the toilet? That's a bit weird, not sure if that complies with the NSPC wet venting rules:


As to your question, I take you are wondering if you can move the shower wye to be downstream of the tub wye. That looks like it would be an easier place to tie in the shower drain given the new location. Once you sort out the above issues, unless you run into some subtlety on the NSPC wet venting rules, that should be fine.

Cheers, Wayne
 

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New Jersey uses the NSPC, which is not so common, so I'm not very familiar with it. My comments:

Your drawing seems to have horizontal dry vents below the floor? That's unusual, and not allowed by the IPC, and with only a limited allowance in the UPC. It looks like the NSPC also has a limited allowance for it, does your DWV comply with that exception?


Also, it looks like the shower is currently wet vented by the toilet? That's a bit weird, not sure if that complies with the NSPC wet venting rules:


As to your question, I take you are wondering if you can move the shower wye to be downstream of the tub wye. That looks like it would be an easier place to tie in the shower drain given the new location. Once you sort out the above issues, unless you run into some subtlety on the NSPC wet venting rules, that should be fine.

Cheers, Wayne
Thank you for your comments Wayne.

I am adding the correct isometric diagram and photo of the physical drain, perhaps it would better convey what I am trying to do.


drain2.png


drain3.jpg
 

wwhitney

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Where's the lavatory? Are you wanting to put the shower drain directly over that 3" line, or can it be to one side?

Per the photo the WC venting is suspect, that horizontal dry vent under the floor is the subject of the first code section I linked to. Per the drawing, the tub vent is similar.

If you want the shower drain directly over the 3" line, that's going to be trouble, you'll have to jog the 3" line out of the way. Otherwise, you should be able to connect the shower drain to the 3" line with a wye in a convenient location, once you get the tub/WC venting figured out and confirm that the shower wye location would conform with your wet venting rules.

Cheers, Wayne
 

Positronus

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Where's the lavatory? Are you wanting to put the shower drain directly over that 3" line, or can it be to one side?

Per the photo the WC venting is suspect, that horizontal dry vent under the floor is the subject of the first code section I linked to. Per the drawing, the tub vent is similar.

If you want the shower drain directly over the 3" line, that's going to be trouble, you'll have to jog the 3" line out of the way. Otherwise, you should be able to connect the shower drain to the 3" line with a wye in a convenient location, once you get the tub/WC venting figured out and confirm that the shower wye location would conform with your wet venting rules.

Cheers, Wayne
Lavatory is the terminal of 3" on the left of the photo. I don't need 2" shower drain to be over 3" line, but rather on the right side of the two joists in the photo. This is needed to accommodate for Schluter off-set subtrade's drain that is positioned 10" from the wall where toilet paper holder is visible.

I suspect it would be hard to add wye to 3", as the way 2" shower pipe is installed, going through joist was probably made to accommodate for proper venting?
 

wwhitney

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Sorry, I'm not seeing the lavatory in the photo. Is the 3" in the top left of the photo (not the one with the rag in it) connected to anything?

If you can update your isometric with the lavatory, and clarify if the cross at the top of the two vertical means a vent through the roof, that would help.

Cheers, Wayne
 

Positronus

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Sorry, I'm not seeing the lavatory in the photo. Is the 3" in the top left of the photo (not the one with the rag in it) connected to anything?

If you can update your isometric with the lavatory, and clarify if the cross at the top of the two vertical means a vent through the roof, that would help.

Cheers, Wayne
I added lavatory to the diagram, and yes, two pipes with crosses on them are vents to the roof.

Earlier you said,
If you want the shower drain directly over the 3" line, that's going to be trouble, you'll have to jog the 3" line out of the way.
How hard would that be? Can I add bend to 3" sewer pipe in order to center 2" shower pipe over the 3" sewer pipe? I will need to do this in order to install 48"x48" Schluter shower base if I were to go with it. I was thinking of getting 38"x60" Schluter shower base, and make it 38"x48" to fit my shower, but apparently manufacturer doesn't recommend cutting more than 4" on each side, so centering the drain would make more sense. Of course if this will become complicated, I would abandon Schluter system approach and go with regular mud shower pan.

PXL_20220214_032319550.jpg
 
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wwhitney

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OK, I can't quite make up my mind whether your existing layout complies with the venting rules under the NSPC. I guess the WC dry vent like that is allowed by NSPC 12.6.2. The geometry of the lavatory/tub connection is a bit unclear on your isometric, but it could be done in a way that either allowed the dry vent for the tub to comply with 12.6.2, or the tub to be wet vented by the lavatory per 12.10. A picture of the the tub/lav piping would help with figuring that out.

That leaves the shower, which you are wanting to move anyway. Easiest thing (venting wise) to do would be to connect the shower to the tub/lav branch before it connects to the 3" WC drain. The shower would be horizontally wet vented by the tub/lav. That can all be done in 2": the NSPC wet venting rules require the wet vent to be one size larger than the minimum vent for the downstream fixture, and one size larger than the drain for the upsteam fixtures, but 1-1/2" is adequate for a vent for a shower, and under the NSPC 1-1/2" can carry 3 DFUs horizontally, 1 for the lavatory and 2 for the tub. So 2" is one size larger as required.

Of course, that leaves the question of whether you could fit that all in the joist bay. The 3x3x2 wye on the WC drain and a 2" wye next to it to receive the shower and the tub/lav. Maybe a picture from above of the critical area, with a tape measure lying across showing the measurement between the joists would clarify that. Plus you mentioned possibly rerouting the 3" line to allow for a shower drain directly over its current location, that would certainly increase the difficulty.

Cheers, Wayne
 
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