3" drain for kitchen sink?!

[mrpriceisright]

Old thread I know, have been researching this for a kitchen and island sink drain /vent (new construction).
As others in the thread point out, this looks like a "Combination waste and vent system", which:
1) until 2018 code change did not allow garb disposer on the drain/vent.
2) requires the drain to be upsized 2 pipe sizes (hence the 3 in pipe I assume).
3) is NOT included in UPC 21 code changes.
This eliminates the need for both the loop vent and aav and simplifies the venting (no length limitations) and meets IPC current code (in this case apart from the extra trap).
I think I'm going to go with it for my case as it seems much simpler than the loop vent and avoids the aav. As I have 2 sinks in the room and have been struggling with the (2) loop vent to drain and vent connections and a way to avoid having 2 vents up in the wall due to the no vent to vent connections below flood level rule. Though I do wish I could do it with 2" instead of 3" down pipe to the main 4" drain.

 

[wwhitney]

I think I'm going to go with it for my case

The UPC doesn't allow combination waste and vent for sinks.

See 910.5 "No vertical waste pipe shall be used in such a system, except the tailpiece or connection between the outlet of a plumbing fixture and the trap."

Also B101.2 "Sinks, lavatories, and other fixtures that rough in above the floor, shall not be permitted on a combination waste and vent system,"

Chapter 9: Vents, California Plumbing Code 2022 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

Appendix B: Explanatory Notes on Combination Waste and Vent Systems, California Plumbing Code 2022 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

Cheers, Wayne

 

[Sponsor]

 

[Jeff H Young]

I was working for a Company and around 2000 to 2002 had a couple tract home jobs in San Diego where they used Studor (AAV) valves with inspectors blessing I was pretty shocked hearing this and never knew to this day if it was proper for inspector to even approve it Around that Time I heard of isolated approval of using them on stuff like out door island kitchens . Still dont know if thats legal under our code or must have AHJ permission . maybe Wayne or others know for sure Id concider an AAV in a pinch you dont bury them so it can be serviced replaced if needed

 

[mrpriceisright]

The UPC doesn't allow combination waste and vent for sinks.

See 910.5 "No vertical waste pipe shall be used in such a system, except the tailpiece or connection between the outlet of a plumbing fixture and the trap."

Also B101.2 "Sinks, lavatories, and other fixtures that rough in above the floor, shall not be permitted on a combination waste and vent system,"

Chapter 9: Vents, California Plumbing Code 2022 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

Appendix B: Explanatory Notes on Combination Waste and Vent Systems, California Plumbing Code 2022 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

Cheers, Wayne

well that's interesting - a real toe stubber.
I thought I'd waded through the upcodes, saw the wc and grease exclusions, vertical limit but don't know how I missed the sink exclusion in that appendix. I'd read that the IRC (2018) and IPC (2021) had changed to allow it (combination vent for island sink).
Looks like I'll have to chat with the inspector (3 hr round trip to county). I have the "structurally impractical to provide venting in a conventional manner" as there is no usable wall within 8 feet of the two sinks. I also wanted to avoid the aav since I'm not sure if it would be approved either. Maybe back to the loop vent.
Seems like the case its most useful for is excluded, particularly considering how wet venting allowed with bathroom sinks/groups is mechanically similar.

 

[Jeff H Young]

Sounds like yours is exactly what island venting was meant for . Is it going to be a lot of work major expence or something to run an island vent ? If you do run an Island vent be sure to follow the upc exactly The cleanouts the use of a combination wye and 1/8 bend and not a santee where noted long sweeps where noted etc. or it will get you reamed!

 

[mrpriceisright]

Sounds like yours is exactly what island venting was meant for . Is it going to be a lot of work major expence or something to run an island vent ? If you do run an Island vent be sure to follow the upc exactly The cleanouts the use of a combination wye and 1/8 bend and not a santee where noted long sweeps where noted etc. or it will get you reamed!

Thanks for all the inputs. I'd seen the multiple CO's, but didn't realize the extra cleanout would need to be a Y but no problem.
After a trip to the county (well I did get the $16k in permits paid), looks like the loop vent is the only answer as they do not allow aav's. (possibly the city (vs county) or a particular inspector would allow it).
The odd thing is that they drew a diagram with the loop vent connecting back to itself (the sink drain part) before entering the main drain with a single connection. I have not seen that arrangement anywhere. In my case the vent will be below/under the slab above the main drain.
Have been trying to avoid having two separate vents from the two loops. both drain correctly but have a single vent go across to the vertical wall. My solution for that is to have a double wye for vent where it drains into the main drain (downstream of sink drains) with the loop vents going into it and have the wall vent connect to the top of the double wye (w 45 before and after to be vertical). In reality I could probably just have back to back wyes for that connection (vent -> loop vent -> main drain). All vent pipes angled to achieve drainage where not in the wall. The house is SIP (solid) wall construction which prevents running vent stack up through outside wall, in most cases (bathrooms, etc) there is an internal wall nearby that can accommodate the vent.
Currently doing the rough in plumbing before slab and just about done.

 

[Jeff H Young]

you tube b g plumbing class " Island venting explained upc 909.1" for a good explanation dont copy anything from ipc or anything that isnt exactly as shown .
Be sure not to stray from the way you build this vent