Help Venting Freestanding Tub

[LetMeVent]

We are currently undergoing a master bath remodel, and want to confirm my plan for venting the new freestanding tub.

The previous bathroom configuration had a corner whirlpool tub framed to abut a single vanity along each side, and the tub drain was wet vented to the lav in the vanity along the far exterior wall via AAV (located in the cabinet underneath the sink).

The new bathroom layout is attached below. Originally, I was planning on venting the new freestanding tub up the new interior wall at the end of the water closet, adjacent to the tub (shown to the left of the tub in the model). However, there is a 2x10 joist directly below this wall (shown in attached model) that should not/prefer not to notch.

So, instead, I am now planning on a straight run of 2" ABS toward the new vanity to tie in as a wet vent (2" instead of 1.5" due to the length of the run needed to tie in to the new vanity drain; would tie in to vanity drain line with 2" wye on the horizontal).

I am located in Ohio and my county uses Ohio Plumbing Code 2017 (which is based off of 2015 IPC with amendments). Wet vents are permitted. Link here: https://up.codes/viewer/ohio/ipc-2015/chapter/9/vents#906

Does this venting method look acceptable? Thanks so much for the shared advice and expertise. This forum, and all of you who contribute are very much appreciated!

 

[LetMeVent]

It appears that the forum has resampled the images I attached, making them quite small and difficult to see/read. I've uploaded full size attachments here as well: https://imgur.com/a/hr8h1gV

To clarify the proposal diagram, the tub would install with a 2" ABS p-trap, then approximately 62" run from the tub's p-trap wier to the wye from the sink drain line. The new double vanity would be installed with 2x1.5x1.5x1.5 double fixture fitting (1.5" dry vent up the wall; 1.5" to each lav; 2" drain down below subfloor, then approximately 24" horizontal toward the tub drain line until they come together at the horizontal wye. Exiting the wye would be an existing 2" ABS drain line going to the homes main horizontal drain line.

Hopefully the link to the larger images helps, and hopefully the above description makes sense. Thanks again.

 

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[wwhitney]

The wet vent looks OK to me.

If you prefer the dry vent, the way it's rendered, it seems like you could go through the joist, use an immediate LT90 to turn towards the main, then an upright combo or wye (or san-tee on its back for the IPC) for the vent takeoff, rolled as required to come up through the bottom plate alongside the joist without notching it. That assumes the joist (1.5" thick) is at one edge of the bottom plate (3.5" wide for a 2x4 wall) and so you can pass a 1.5" vent (1.9" diameter) alongside the joist within the footprint of the wall. If the joist is closer to center, then you'd possibly have to fir out one side of the wall.

Also, while there's something to be said for avoiding the code-allowed D/6 depth notch in a joist, I think that a more minimal notch is not of concern. E.g. 3/4" notch depth at the edge of the joist, 0" depth at joist mid-thickness (small partial width notch of triangular cross section).

But I don't know if that's any better than the wet vent option.

Cheers, Wayne

 

[LetMeVent]

wwhitney,
Thanks very much for the quick response.

If you prefer the dry vent, the way it's rendered, it seems like you could go through the joist, use an immediate LT90 to turn towards the main, then an upright combo or wye (or san-tee on its back for the IPC) for the vent takeoff, rolled as required to come up through the bottom plate alongside the joist without notching it. That assumes the joist (1.5" thick) is at one edge of the bottom plate (3.5" wide for a 2x4 wall) and so you can pass a 1.5" vent (1.9" diameter) alongside the joist within the footprint of the wall. If the joist is closer to center, then you'd possibly have to fir out one side of the wall.

I tried to render the joists as accurately as possible, but the way it appears on the attached model might be deceiving. As you've correctly surmised, it is a 2x10 joist (1.5" thick) and a standard 2x4 interior wall (3.5" bottom plate). In actuality, the joist is almost directly centered under the location for the bottom plate (at most, the joist is offset 0.25" toward the right side/tub side of the wall). So, I don't see any way to dry vent without significant notching. I also contemplated moving the wall a few inches one way or another (or furring it out)... but the measurements in here are already tight. Shifting the wall away from the tub (or furring the inside of the water closet) would necessitate moving to a smaller door on the water closet (that door is already 28" door). Shifting the wall toward the tub (or furring the outside of the water closet) will eat into the very limited space for the tub. The tub is a 67" stone soaking tub, and as it stands, will have roughly 5-6" clearance on each side (depending on final wall surface treatment). Any smaller, and it may make access/cleaning around the sides of the tub quite difficult. Ultimately, those are the reasons that I thought moving to a wet vent through the lav might be the "best" remaining option.

Obviously I am still open to suggestions if there is a better solution out there! Thanks!

 

[wwhitney]

Based on my crude drawing below, with 1/2" drywall and 3/4" baseboard, a 2" OD pipe (vent) would just fit between the centered joist and the visible face of the baseboard. That's based on a 3/4" subfloor, any finish floor on top would provide more clearance.

Rather than make things so tight, as I suggested it would be fine to notch out a 3/4" x 3/4" right triangle at the top of the joist. (The area that the red pipe would intersect in the joist if you moved it 3/4" to the left.) Even 1" if required. [The IRC would allow a 1.5" x 1.5" rectangular notch in a 2x10 away from the center third of the joist, if I recall. A 3/4" x 3/4" right triangle is 1/8 as much of the cross-section.]

BTW, I'm not saying this is better than a wet vent, I'm just suggesting you do have options to do a dry vent if you want, even with the centered joist.

Cheers, Wayne

 

[LetMeVent]

Wayne,
Thanks once again for the insight, as well as the visual. I had forgotten to account for baseboard/molding when considering a dry vent through that water closet wall. That does provide for a little bit more room/less notching. In addition, I will be tiling over the subfloor as well (thinset + uncoupling membrane + thinset + tile = approximately 1" thickness on top of 3/4 subfloor), which also provides a slight buffer in the room required for notching as well. So... I suppose the dry vent at that location is feasible after all.

All of that being said... now the question becomes... is it worth it!? What began as a headache in determining how I can reroute my venting as a result of the joist/wall placement, has led to a workaround solution that does offer some benefits.
Now it's either:
-bore 2 joists over, then 90 toward main drain, vertical takeoff (>45deg) with wye, bore through floor and bottom plate, possible small notch in joist, dry vent to attic, then horizontal to tie into existing vents (plus new drain and vent for new double vanity either way)
-or-
-straight run 2" toward main, tie into existing plumbing + new lav plumbing (no boring, no notching, no second dry vent to tie in)

It almost seems like the "workaround" solution that began as a headache is the better/simpler option at this point (at least in terms of material/labor/cost/efficiency). Unless there's any reason not to... I'll probably go with the wet vent to the lav... which I'm very glad to see was confirmed as a viable layout here.