Is this a correct wet venting design ?

[Mini Me]

I am not sure if I properly understand the wet vent concept so here is the question The current bathroom apparently has no dry venting. I am moving the sink from the point marked on the wall just behind where it says '2"(to be confirmed)' to the position shown in the picture ("new sink)" The piping is not much longer in this layout. I can upgrade everything to 2"

Will this comply with a wet venting design ? ( I am assuming that in the past the wet venting was via the soil stack or it was not there at all and the design is not valid)

 

[wwhitney]

Wet venting is a way to share a single dry vent among several related fixtures in proximity. If you have no dry vent at all, then you can't wet vent. If you add a dry vent to the lavatory (connected to a pipe through roof, or to AAV if allowed in your jurisdiction), then the lavatory could wet vent the shower.

There may be a stack venting solution, but I'm not so familiar with that.

Cheers, Wayne

 

[Sponsor]

 

[Mini Me]

Then I am not sure how it worked before the demolishion
I think that the 2" segment that goes toward the soil stack could have worked as wet venting for the shower and sink

this is the old layout -the green segements were not there and they are not there today. This worked. How did it work ?

here is the situation today

 

[Reach4]

For new stuff, with US codes, the line below the lavatory sanitary tee (wet vent) and shower drain would all have to be 2 inch. If retrofitting, you tend to do what you can. 1.5 usually works in practice.

 

[Mini Me]

thanks for the feedback
from what you are saying I understand that the existing layout was OK even with 1.5" all the way
@wwhitney seems to disagree with this
Since it worked before I am considering adding an AAV under the sink ...that should keep me safe.

 

[wwhitney]

Reach4's comments seem to be predicated on there being an unshown dry vent at the top outlet of the lavatory sanitary tee. In which case you would have a wet vent for the shower. But if there's no dry vent for the lavatory, you need to at least add an AAV, if they are allowed in your jurisdiction.

Cheers, Wayne

 

[Mini Me]

I am wondering if instead of breaking the floor I could do this
just run ABS across the walls (1) back to (2) which is the existing plubing for the old sink

I am trying to build this I hope I can sneak the ABS under the shower head/panel plumbing

 

[wwhitney]

For new stuff, with US codes, the line below the lavatory sanitary tee (wet vent) and shower drain would all have to be 2 inch.

If I'm reading IPC 912.3 correctly, for a single lavatory wet venting a shower, so only 1 DFU is discharging into the wet vent, the wet vent can be 1-1/2".

Cheers, Wayne

 

[Mini Me]

Reach4's comments seem to be predicated on there being an unshown dry vent at the top outlet of the lavatory sanitary tee. In which case you would have a wet vent for the shower. But if there's no dry vent for the lavatory, you need to at least and an AAV, if they are allowed in your jurisdiction.

Cheers, Wayne

I guess an AAV won't hurt...what puzzles me is how it worked before

 

[James Henry]

A shower is between 2 and 5 DFUs. A 2" drain will be required.

 

[James Henry]

If the lav has no vent the fixtures probably worked because their so close to the vent stack.

 

[Reach4]

Reach4's comments seem to be predicated on there being an unshown dry vent at the top outlet of the lavatory sanitary tee. In which case you would have a wet vent for the shower.

A reasonable assumption I think, unless the original was very old.

I guess an AAV won't hurt...what puzzles me is how it worked before

There should have been a vent. Did you discover that there was not one? But if there was not one, the lavatory trap is likely to get refilled anyway, since lavatory draining often involves slow water flow at the end. Plus what Henry James said if the trap arm slope was carried on to the stack.

 

[wwhitney]

A shower is between 2 and 5 DFUs. A 2" drain will be required.

IPC and UPC differ on this for a lavatory wet venting a shower:

IPC, shower up to 5.7 gpm, 2 DFU's, minimum trap/drain size 1-1/2". Lavatory, 1 DFU. Horizontal wet vent carrying the discharge of only 1 DFU, minimum size 1-1/2". Maximum DFUs on 1-1/2" horizontal drain is 3. Everything could be 1-1/2".

UPC, shower minimum drain size 2". Wet vent minimum size 2". Everything from the lavatory sanitary tee downstream has to be 2".

Cheers, Wayne

 

[James Henry]

Your not a plumber and your wrong.

 

[wwhitney]

From the 2018 UPC (as amended by California, but I don't think they've amended the relevant sections)
https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/7/sanitary-drainage#7
https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/9/vents#908.2.2

Table 702.1 - Shower, Private 2" minimum trap, 2 DFUs
Table 703.2 - Maximum DFUs on horizontal drain: 1-1/2" 1 DFU, 2" 8 DFUs
908.2.2 - Horizontal wet vent size: 2" for up to 4 DFUs discharging into the wet vent

So we agree under UPC everything has to be 2". Contrast that with the 2018 IPC (unamended by Colorado):
https://up.codes/viewer/colorado/ipc-2018/chapter/7/sanitary-drainage#7
https://up.codes/viewer/colorado/ipc-2018/chapter/9/vents#912.3

Table 709.1 - Shower, flow rate up to 5.7 GPM, 1-1/2" minimum trap, 2 DFUs
Table 710.1(2) - Maximum DFUs on horizontal branch: 1-1/2" 3 DFUs, 2" 6 DFUs
Table 912.3 - Horizontal wet vent size: 1-1/2" for 1 DFU discharging into the wet vent; 2" for 4 DFUs

Under the IPC, everything can be 1-1/2" for a single lavatory wet venting a shower not exceeding 5.7 GPM.

Cheers, Wayne

 

[James Henry]

Where your screwing up is that you think you can mix and match the wet vent code and the drainage code and you can't. Look at the wet vent sizing table. Lav plus shower equals 3 DFUs. 4 DFUs on 2" drain. Your wrong. If you don't see it you don't understand the theory behind wet vents.

 

[wwhitney]

Where your screwing up is that you think you can mix and match the wet vent code and the drainage code and you can't. Look at the wet vent sizing table. Lav plus shower equals 3 DFUs. 4 DFUs on 2" drain. Your wrong. If you don't see it you don't understand the theory behind wet vents.

I considered that interpretation, but I don't think that's correct.

The phrase used is "fixture unit discharge to the wet vent". The only fixture discharging to the wet vent is the lavatory. The wet vent ends at the wye point of the wye fitting, the shower itself does not discharge into the wet vent. So there is only 1 DFU discharging into the wet vent.

Under your interpretation, there would always be at least 2 fixtures discharging into the wet vent, so it would always be at least 2 DFUs. Then there'd be no reason for the first line in IPC table 912.3, which says a 1-1/2" wet vent is sufficient for 1 DFU discharging into the wet vent.

Same thing also applies to the UPC. Say you have a dry-vented lavatory (1 DFU), then a wet vented shower (2 DFUs), and a wet vented toilet (3 DFUs). You can use a 2" pipe from the lav san-tee to the wye where the toilet comes in; 3" for the toilet drain on both sides of the wye. If you counted the 3 DFUs for the toilet in sizing the wet vent, you'd be at 6 DFUs, and you'd have to use 3" everywhere. Which is not the case.

Cheers, Wayne

 

[James Henry]

Thanks for playing.

 

[wwhitney]

Thanks for playing.

I'm going to assume that means "Gee, you're right." : - )

Cheers, Wayne

 

[Reach4]

The phrase used is "fixture unit discharge to the wet vent". The only fixture discharging to the wet vent is the lavatory. The wet vent ends at the wye point of the wye fitting, the shower itself does not discharge into the wet vent.

See picture on page 12 of https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf