Do I need another dedicated vent for the toilet?

[Tomski]

Long time reader but first time posting and hope you guys won't mind yet one more " is my layout OK? " question. I'm in California so UPC.

Getting ready to start ripping out concrete to add a 3/4 bath on slab. My layout is pretty straightforward and I think I am OK but I was looking at some new houses under construction and it appears the toilets are all individually vented. However, theses houses were on slab foundations and I couldn't be sure how things were put together below. I have read that venting requirements for a toilet could depend on the order it's in in relation to the other fixtures along the drain and since mine is last I think I'm good but would like to make sure before cutting up the slab. I have been unable to get a response from the local building department and due to covid, there is no counter service.

Really appreciate your input.

 

[Reach4]

I think the wye for the UPC horizontal dry vent gets rolled a bit to make the horizontal dry vent higher than the trap arm. I don't know how high that needs to go.

 

[Sponsor]

 

[Jeff H Young]

Shower vent may not be legal , and should be able to be wet vented so that vent should eliminate. but I think w/c needs to be furthest upstream fixture requiring wyeing off befor the w/c, so confirm that but shower vent not good
Actualy took a look at code just the shower vent is issue the rest is good

 

[wwhitney]

One option:

- Delete the shower vent.
- Increase the lav dry vent to 2".
- Ensure the shower trap arm (from trap outlet to connection to lav drain) is no more than 60", with no more than 2" fall. Reroute the lav drain if necessary to do this.

Now it's a UPC compliant horizontal wet vent. Or you can proceed as you've drawn if you:

- Upsize either the lav dry vent or the shower dry vent to 2" (the WC requires a 2" vent). If you upsize the shower dry vent, you could arguablely downsize the lav drain to 1.5", as it is no longer required to be a wet vent.
- Roll the wye for venting the shower up to at least 45 degrees above horizontal. Use a long turn 90 where the vent turns up into the wall.

Cheers, Wayne

 

[Jeff H Young]

Good catch wayne minimum vent on w/c 2 inch. I dont think the shower would fly as providing a vent for W/c dont see it as a choice since dry vent is below flood level. and a perfect soulutin is to use the lav . Agree though delete shower vent

 

[wwhitney]

I dont think the shower would fly as providing a vent for W/c dont see it as a choice since dry vent is below flood level.

Seems to me those are two different requirements that do not interact.

If the shower is individually dry vented, and structural conditions preclude the vent takeoff rising to 6" above the flood rim before going the horizontal, the UPC allow a lower horizontal vent, as long as the lower than normal portion is plumbed in a drainage pattern.

If the shower is dry vented, it can wet vent the WC.

I don't see an issue.

Cheers, Wayne

 

[Tomski]

Thank you all!

As long as I'm not required to have a clean out I will probably go with Wayne's option #1 since I'm within the 60" on the shower trap arm.

One last question. In light of the fact that I saw individual 2" vents on all of the under construction houses (4 of them) that I saw locally, is there any chance that our local building department has some added restrictions in regard to toilet wet vent rules? Again, I could not see the whole setup as they were on slab and already poured. Very frustrating not being able to get an answer directly from them.

 

[Jeff H Young]

Seems to me those are two different requirements that do not interact.

If the shower is individually dry vented, and structural conditions preclude the vent takeoff rising to 6" above the flood rim before going the horizontal, the UPC allow a lower horizontal vent, as long as the lower than normal portion is plumbed in a drainage pattern.

If the shower is dry vented, it can wet vent the WC.

I don't see an issue.

Cheers, Wayne

Yes but structural conditions do not keep the shower from being vented properly by using the lav that can be avoided. So there is no argument that structural condition requires it to be vented in such way. Basically the argument would be to vent it like that because that's the way you would rather do it, not a hardship , inconvenience or any thing, that's the kind of reason inspector will fail

 

[wwhitney]

Good point, the too-low horizontal shower dry vent could be disallowed on that basis. [If using the lav drain to wet vent the shower required a really circuitous lav drain path, it becomes a judgement call as to at what point it's too circuitous and the too-low horizontal dry vent should be allowed.]

And I guess what you are saying is that if the horizontal shower dry vent is of dubious compliance, best not to rely on it for venting the WC. So size the lav drain and vent for wet venting the WC regardless.

Sounds good.

Cheers, Wayne

 

[Jeff H Young]

I could see running the 2 inch vent on the lav and rolling up the shower vent as well in 2 inch but seems it might be safer from an inspection point of view to delete the shower vent.

 

[Tomski]

Thanks again Jeff, Wayne and Reach4. I feel much better about starting the demo. I was a physics major in college and a DIY'er for a very long time but I swear, wet venting rules were giving me fits.

 

[Jeff H Young]

Thanks again Jeff, Wayne and Reach4. I feel much better about starting the demo. I was a physics major in college and a DIY'er for a very long time but I swear, wet venting rules were giving me fits.

Me too understanding venting still a challenge especially with horizontal wet venting ( which didn't used to be allowed in UPC) , and other venting which can be allowed or not depending on opinion of inspector . Then a simple plan like yours has both . I don't get to see a lot of new home plumbing my guess is a lot of guys shy away from horizontal wet venting that don't understand it that well .