Toilet and Shower Plumbing Question / Wet Venting

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Contracheatcode

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Need help to ensure proper venting of toilet and shower that share same vent.

See photos below:

Question 1) does this configuration work? Specifically can I wet vent the shower drain via the toilet black water 3 inch pipe?

Question 2) If yes, where would you recommend connecting the shower drain to the toilet drain?
Box 1: which is BEFORE the drain drops about 12 inches and turns 90 degrees?
Box 2: which is AT the drop? I would need a 90 degree street with a horizontal 2 inch inlet for shower drain. Do they even make that?
Box 3: which is right after the drop/ turn? I think can fit the shower drain p-trap and have it smoothly turn down into a wye in box 3 area.

E4A6A9A1-566B-41D0-95A1-B18E95FF27F2.jpeg



Thanks to all.

Mike

1BA11954-6B08-427F-9047-3A548890B261.jpeg
 
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wwhitney

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1) No, not under the UPC, which California uses.

But you could put a 2" dry vent on your 2" shower drain (within 60" of the trap, before the trap arm falls more than 2"), and then join that to your 3" WC drain (with 72" of closet flange, no height restrictions), and the dry-vented shower would wet vent your WC. The dry vent has to come off the shower trap arm vertically (at least 45 degrees above level) and rise vertically until 6" above the shower flood rim, so you'd need to route the shower trap under or alongside a wall for the vent.

Cheers, Wayne
 

Contracheatcode

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1) No, not under the UPC, which California uses.

But you could put a 2" dry vent on your 2" shower drain (within 60" of the trap, before the trap arm falls more than 2"), and then join that to your 3" WC drain (with 72" of closet flange, no height restrictions), and the dry-vented shower would wet vent your WC. The dry vent has to come off the shower trap arm vertically (at least 45 degrees above level) and rise vertically until 6" above the shower flood rim, so you'd need to route the shower trap under or alongside a wall for the vent.

Cheers, Wayne

Thanks Wayne.

I need some help thinking through how to vent the shower before entering the WC drain.

The long wall is exterior and I cannot vent there.

Below is a picture of more area. You can see I was planning to vent the WC up the left wall. Nothing glued together yet. So options open.

DCDCC20C-726A-4D73-BF01-106D8EBA6D86.jpeg
 

wwhitney

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Simplest would be to have at least a wing wall between the WC and shower that would hold the shower vent, rather than having glass run to the exterior wall. You'd need the wing wall to be at least 6" rough--a 2x4, a 3" space for the hub on a 2" fitting (if any are necessary), and another 2x4 at the end. Maybe better to make it 9", for a double 2x at the end for fastening the glass to, and a little extra space around the 2" vent.

Otherwise, you can run the 2" shower drain over to the wall to a san-tee if the trap arm (trap to san-tee) would be less than 60". Once the shower drain goes horizontal again, I would think it would be simpler to join the WC to the shower drain closer to the WC, before the WC drain does a 90. They would join with a horizontal wye.

If you want to minimize the shower drain elevation loss at the vent takeoff in the wall, you can start with a street san-tee into a LT90 (or a san-tee connected to a street LT90). You can also rotate that san-tee/LT90 assembly 45 degrees about the san-tee side entry, using a 45 at the top entry to make the vent vertical. That would reduce the elevation loss, but only works for very close to a 180 degree change of direction in plan.

Cheers, Wayne
 

Contracheatcode

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I think I follow. So something like the below picture.

The shower gets it’s own vent using the WC wall via a san-tee at a 45 angle. The air vent goes vertical in WC wall. That shower drain then connects to the WC drain via the 180 turn that is sloped at 45 degrees. It connects to WC drain via wye on its side.

I assume I still need the WC vent that is just upstream. If not, would it hurt to keep it? If I kept that dedicated WC vent it would not have to wet vent off the shower drain.

A7D842E3-4254-4A6A-A26D-8127E1A7CBDD.jpeg
 

wwhitney

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Let's see if I understand correctly: the WC is on the other side of the wall on the left, and the shower extends to that wall. [My comment about a wing wall was based on the idea the WC was on this side of the wall.] The upright wye by where the bottom plate has been removed is a dry vent for the WC. (It needs to be 2", and will it really reach the wall before emerging from the slab? Looks close.)

In that case the above layout is all fine. You don't need the WC dry vent if the shower dry vent is 2" and you connect the shower drain to the WC fixture drain within 6' of the flange. Conversely, if you do provide a 2" WC dry vent, then the shower dry vent only needs to be 1.5". And if you have two dry vents in that stud bay, then can combine at any elevation at least 6" above both flood rims (so controlled by the WC bowl height).

Cheers, Wayne
 

Contracheatcode

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We are on the same page:

Yes the WC vent is perfectly center in stud bay. It’s just not glued up yet so might look too far away.

Unless there is a reason for the shower vent to be 1.5 inch, then can I just got with a 2 inch vent and connect the shower and WC vent lines 1/2 way up wall (which would be more than 6 inches above bowl height)?

Also, confirming no need for clean out on the 180?

Thanks so much Wayne.
 

wwhitney

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Sure, you can use a 2" shower dry vent and a 2" WC dry vent and combine above the specified height.

As to cleanouts, I've not studied those rules, but they are here: https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/7/sanitary-drainage#707.0

I would say that the san-tee / LT90 subassembly would not count as a horizontal change of direction as they are both "vertical". I could also imagine that there'd be an upside to making the WC vent 3" and putting in a cleanout fitting facing the WC room with an access plate. It could reduce to 2" above the cleanout fitting. Not clear on whether the above rules require such a cleanout.

Cheers, Wayne
 
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Contracheatcode

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Thanks Wayne for all your help. Here’s the final product. I’d give myself a solid A.

The only slight issue could be that they wye is only 2 inches about the toilet bowl top. I am going to call that good enough, unless you think otherwise.

F8A5AEBB-F888-426B-992C-DC0EC7A4E584.jpeg


Thanks. Mike
 

wwhitney

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The "crotch" of the wye is supposed to be 6" above the toilet flood rim. Whether 2" suffices is not my call to make.

I guess if you had a blockage in the 3" line between the WC vent takeoff and the 3x2 shower/WC drain wye, and waste backed up in the WC vent to the toilet flood rim, then it would only be 2" away from spilling over and flooding your shower.

Anyway, that's the scenario that drove that rule, to my understanding.

Cheers, Wayne
 

Contracheatcode

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The "crotch" of the wye is supposed to be 6" above the toilet flood rim. Whether 2" suffices is not my call to make.

I guess if you had a blockage in the 3" line between the WC vent takeoff and the 3x2 shower/WC drain wye, and waste backed up in the WC vent to the toilet flood rim, then it would only be 2" away from spilling over and flooding your shower.

Anyway, that's the scenario that drove that rule, to my understanding.

Cheers, Wayne

Exactly.

I’ll sleep on it and see if it’s going to drive me crazy.


Mike
 

Contracheatcode

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Hey Wayne,

New question:

I am installing recessed medicine cabinets behind vanity. There is a dry vent for sink that i will shift to side stud bay and then back with 45s. There is also a wet drain from sink upstairs that runs in same stud bay that also needs to shift.

I assume a can shift the wet drain from upstairs with 45s as well? Any issues with that shift?

Thanks,

Mike
 

wwhitney

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Vents can shift with 45s when less than 6" above the fixture flood rim. They can shift with 45s or 90s when more than 6" above the fixture flood rim.

Drains can shift with 45s or 90s. If using 90s, you need a LT90 when the drainage goes from vertical to horizontal, but a quarter bend will suffice when the drainage goes from horizontal to vertical. Shifting with 45s is perhaps better.

Drilling studs at a 45 is a little challenging, and problematic in a load bearing wall, but fine in a non-load bearing wall. If you are just shifting within a stud bay, go with 45s.

Cheers, Wayne
 

Contracheatcode

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Thanks Wayne. It’s a load bearing wall to my garage. But they are 2x6 studs and the medicine cabinet only goes in 4 inches. So I will put a 2x6 up against the back for support and go with the 45s all the way around .

Thanks always.
Mike
 

Jeff H Young

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we always shoot for that 6 inch height above flood level but you'll never get a clog at 2 inches above. you could have put a couple more 45s and met code but its already done and passed inspection so sleep well!
 
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