We recently started a master bath remodel project and ran into a snag with the planned DWV system. The following image shows the plumbing behind the wall:

[drive.google.com]

In the image, #1 is the hall bath sink drain (1.5", #2 is a drain/vent (2.0", #3 is the vent for basement plumbing (2.0", #4 is the vent for the master shower (1.5" and #5 is the vent for the hall bath tub-shower combo.

The plan is relocate one of the two master bath sinks to this wall (near side). Initially, not knowing what was behind the wall, we were going to tie the sink drain/vent in at #2 but unfortunately the sink centerline falls between vents #4 and #5 (would have to cross #4 and #3 to get to #2). The green lines in the following image show the new proposed plumbing modification:

[drive.google.com]

As far as code goes, our county follows UPC 2006. We have a current permit for the project.

The new plumbing would be 1.5" piping that drops below floor level into a 2.0" drain which enlarges to a 3.0" drain about 3 ft downstream of where the new tie-in would be. I've calculated the fixture load going through the stud with the question mark ("?" to be 2 + 1 + 2 = 5. Currently there's 2.0" piping through the 3.5" stud which I believe is not legal with building codes (non-load bearing interior wall), so may have to bring that up to code (max 2.25" hole, 0.625 from edges) by downsizing the stud pass-through to 1.5" piping.

Request feedback on if this looks acceptable or other proposed solutions.

Thank you.

troy

i would not worry about the size of the vent.
i would however move the 1 1/2 san tee up to the horizontal portion of the vent header.
vent can not run horizontal until it is 6 inches higher than the flood rim of the fixture it serves. so roughly 42 inches off the floor.

Thank you for the quick response Packy.

I had originally looked at putting the sanitary-t on the horizontal between vents #4 and #5 but dismissed it due to the lack of horizontal clearance between vents, but I wasn't originally thinking about putting in the offset/dogleg in vent #5 and think it will probably work with that.

The centerline at the top of vent #5 is approximately 41 inches, uphill slope (1/4" per foot) from there.

v/r
troy

it looks like a 2 x 1 1/2 x 1 1/2 san tee with a street 90 in the end would work.

Packy, problem I'm running into is the centerline distance between vent #4 and the new vent is only 3.75". If you horizontally butt the hubs of two 1.5" san-tees up to each other, I believe the outlet centerlines are about 4.75", so the pipes are about 1 inch too close to each other. I could probably angle the new vent slightly, but not enough to correct for a 1" alignment error. Thank you for your assistance.

Here's an illustration of the issue:

[drive.google.com]

v/r
troy



Edited 1 times.

A st. tee would gain you 3/4".

you can't make that small offset with street 22's ?

Is the shower drain 2"? If yes, can you replace the shower vent pipe with 2", install a sanitary tee in the vertical section for the lavatory and wet vent the shower through the lavatory?

Thanks North Carolina Plumber, that may just do it.

Packy, not sure I follow on how to apply the street 22's

Steve, shower drain is 2" and I see what you mean by #4 as a 2" vent, my main concern is when the 2" goes horizontally through the standard 2x4 stud I don't think it complies with local building codes (holes less than 60% of stud width, no closer than 5/8" to edge, for an interior, non-load bearing wall). I'm unsure if the inspector will fail for this since the home was built this way, but predicting he might.



Edited 1 times.

The 2" wet vent would stop at the lavatory tee and then continue as a dry vent above the tee in 1½". As to the oversize hole, code allows doubling the stud, so either that or possibly a metal "stud shoe" could be used to reinforce the stud, if inspector wants to address the existing issue.

Steve, below the floor I believe the shower is already wet-vented, effectively, through the 2" pipe #2 (about 56" down stream of drain). The 1.5" pipe #4 is currently serving as a dedicated (dry) vent for the shower (about 50" down stream of drain). So question now is, could I simply put a 1.5" san-tee in the 1.5" vent pipe #4, converting it to a drain vent for a new sink? This would allow the shower to wet-vent through both 2" pipe #2 and 1.5" pipe #4 at the expense of have a dedicated dry-vent.

technically a 'wet vent' being a pipe that serves as a drain and a vent must be increased one pipe size.
but it will work just fine the way you propose to do it..
especially since a vanity drain is only 1 1/4 inch..

Steve and Packy, first off thank you both very much for your inputs. Here's an illustration of the new proposal:

[drive.google.com]

In the illustration, #1 is the hall sink drain (1.5", #2 is the main vent (2.0", #3 is the basement bath vent (2.0", #4 is the current master shower vent (1.5", #5 is the hall tub/shower vent (1.5", #6 is the master shower drain (2.0" and #7 is the hall tub/shower combo drain (1.5".

If I understand wet-venting code correctly, if you completely removed vent #4, the shower drain #7 would be legally wet-vented through main vent #2. So, if we added a single sink vanity drain (stub-out shown in green), I'm thinking technically it would not be required to treat the drain side of #4 as a wet-vent. Otherwise, the drain side of #4 would need to be 2.0".

Am I on track here or do you see a better way?

Thanks so much for your help.

troy

the toilet is wet vented thru lav 1. the shower also is wet vent thru lav 1. i suspect the shower trap is too far from the vent connection so they individually vented the shower thru 4. your connecting to 4 for a sink drain is probably 98.99% legal but some inspector somewhere would not like it. (i approve)..

The existing underfloor venting isn't legal, with the dry #4 shower vent and dry #5 laundry vent being run flat below the "6 inch above flood level of the fixtures" requirement. If the shower drain is less than 6' from the wet vent, you could disconnect the #4 vent from the shower drain, install a wye downstream of everything and use #4 as a stand alone drain and vent for the lavatory.

Thanks for the inputs Steve and Packy.

Ok, so given the code violations in the existing (new construction 2004) plumbing, and also given that access to the below floor plumbing is easy now (unfinished basement, but completing soon), I think it's best to bring everything up to code and hopefully make things a bit cleaner.

The following illustration is the current plumbing installed during construction in 2004:

[drive.google.com]

1. Hall Bath Sink Drain (1.5"
2. Main Vent (2.0"
3. Basement Bath Vent (2.0"
4. Master Shower Vent (1.5" - code violation, horizontal vent run below floor
5. Hall Tub/Shower Vent (1.5" - code violation, horizontal vent run below floor
6. Hall Tub/Shower Drain (1.5"
7. Master Shower Drain (2.0"
8. Master Toilet Drain (3.0" - venting questionable since all ties have horizontal runs below floor
9. Hall Toilet Drain (3.0" - venting questionable since all ties have horizontal runs below floor

The following illustrations show the proposed corrections and adjustments:

[drive.google.com]

[drive.google.com]

1. Hall Bath Sink Drain (1.5"
2. Main Vent (2.0" - to act as wet vent for shower #7
3. Basement Bath Vent (2.0"
4. Master Sink Vent (2.0" - to act as wet vent for hall toilet #9 and master toilet #8
5. Hall Tub/Shower Vent (1.5" - added to correct for vertical venting
6. Hall Tub/Shower Drain (1.5" increase to 2.0"
7. Master Shower Drain (2.0"
8. Master Toilet Drain (3.0" - wet vented through #4 sink drain
9. Hall Toilet Drain (3.0" - wet vented through #4 sink drain

Does the proposed plumbing look up to code? Any issues you see?

Thanks again for your help.

Per 2006 UPC, 804.1, the laundry standpipe trap shall be located 6"-18" above the floor. 908.4 states only the fixtures of the bathroom(s) shall enter the wet vented horizontal branch, so the laundry drain would need to tie in downstream of the hall toilet wye. The standpipe shown appears to be 1½" with a 2" trap. The standpipe needs to be 2" per Table 7-3. Newer codes prohibit toilet #9 tying in upstream of #4.

Thanks Steve.

I've seen a lot of examples out there of a water closet (toilet) draining upstream of a wet vent, as in #9 toilet using #4 vent. The code about being "downstream" is a little confusing to me. In some examples I've seen, it seems to refer to being at a lower flood level, in others it's suggestive of downstream horizontally in the branch drain. I suppose the concern is siphoning, but would bet under the right conditions that can occur no matter which side of the vent the toilet is on. It doesn't seem like there's any way to drain 2 toilets using the same wet vent if both have to be downstream of the wet vent since both have to be inline draining into a wye (which effectively puts one of the toilets upstream of the other) and all other fixtures would have to drain upstream of the wet vent since placing them downstream of a toilet could force them into the role of a downstream wet vent. That just doesn't make a lot of sense to me.

We're subject to UPC 2006 here.

There's no laundry tie-in in this plumbing, it's bathroom vanity sinks draining on #2 and #4, a bathtub/shower combo draining at #6, and a shower draining at #7.



Edited 2 times.

The toilet drain location in a wet vent system didn't show up until the 2009 UPC. I didn't read the list through, to see the tub/shower drain description and thought by the picture, it was for a clothes washer(oops).

Ok folks, here's the latest revision:

[drive.google.com]

[drive.google.com]

1. Hall Bath Sink Drain (1.5"
2. Main Vent Stack (2.0" - to act as primary wet vent for shower #8
3. Basement Bath Vent (2.0"
4. Master Sink Drain/Vent (2.0" - could act as backup wet vent for shower #8
5. Master Toilet Vent (2.0" - will serve as wet vent for toilet #9
6. Hall Tub/Shower Vent (1.5" - added to correct for vertical venting
7. Hall Tub/Shower Drain (1.5" increasing to 2.0"
8. Master Shower Drain (2.0"
9. Hall Toilet Drain (3.0" - wet vented through #5, wet part is tie through #10 toilet drain
10. Master Toilet Drain (3.0" - dry vented through #5

Hopefully I've got it covered this time. Anyone see issues with this?