Is this the best way to vent this L shape bathroom following UPC code?

[AJRiddle]

I live in an old house and had to gut the old bathroom and plumbing to it (because it was done horribly wrong and lots of rotten wood needed repaired as well).

This is the layout of the new bathroom, with the main drain line coming from the top of the picture (behind the sink/shower):

This is the plan I came up with hoping to use the existing hole in the top/bottom plates and to the roof. It is a horizontal wet vent system for the bathroom group.

The main line it would connect to is 4" so I've opted to keep the trap arm to the water closet as 4". The shower drain and vent is 2" pipe and the small section for the trap and arm of the lav is 1.5".

 

[Reach4]

Looks good.

 

[Sponsor]

 

[wwhitney]

UPC requires a 2" vent for a WC, so the green pipe needs to be 2".

Cheers, Wayne

 

[AJRiddle]

Okay so after heading back down to the crawlspace with some fittings I made some design changes.

Do these 2 plans still work with UPC?

If it doesn't have any flaw I'm missing, Option B would be my preference based on fewest fittings and ease of install.

 

[Reach4]

I am pretty sure those are good, but for UPC, there is a limit in how long the 4-inch pipe runs before the blue vent. That limit is 5 ft, but I am not sure how that 5 ft is measured.

One exception... I don't think that drain plug at the bottom of of your shower trap U is desirable. That may not be on the part you were intending to use, but was just there on the image.

I suspect most would use 3 inch pipe, with many using a 4x3 closet bend mounting the closet flange. But 4 inch the whole way is certainly good.

 

[wwhitney]

Either one is fine with the UPC as long as the total run of pipe (counting both vertical and horizontal portions) between the closet flange and the 4x4x2 wye (counting the length of the barrel of the wye between the straight inlet and the 2" branch inlet) is at most 72".

Cheers, Wayne

 

[John Gayewski]

Looks good.

 

[TroyM]

I have more of a question than a statement. I’ve seen a bunch of YouTube videos, talking about wet venting, and dry venting a water closet. If you’re feeding a lavatory sink in a 2 inch wet vent some say to keep it flat to make it a wet vent other say roll it up 45°
Specifically one said when you roll it up 45°. You’re introducing the water in the upper portion of the 3 inch trunk line from the water closet and it’s not allowed. It would seem to me a wet vent needs to remain flat and not rolled up to keep the water in the bottom of the pipe and the vent air at the top

 

[AJRiddle]

So after starting the project I've found some things are in the way of my original horizontal vent plan. My updated attached plan images would fit perfectly in the tight spaces I have got to work with in my old house's crawlspace but I'm not sure if the wet vent I have here with the shower coming off from the vertical portion is allowed with UPC 2018.

 

[John Gayewski]

So after starting the project I've found some things are in the way of my original horizontal vent plan. My updated attached plan images would fit perfectly in the tight spaces I have got to work with in my old house's crawlspace but I'm not sure if the wet vent I have here with the shower coming off from the vertical portion is allowed with UPC 2018.

That works

 

[AJRiddle]

That works

Anything you would change or anything to be cautious about? Planning on priming and gluing tomorrow if all goes well

 

[John Gayewski]

Anything you would change or anything to be cautious about? Planning on priming and gluing tomorrow if all goes well

Other than 4" being oversized for a toilet. I'm told in the 2024 upc they changed the amount of toilets that can fit in a 3" pipe, from 5 to 6. I haven't looked that up since I don't have a 2024 book, but 4" pipe can do something like over 50 toilets. Not much reason for 4" pipe to be ran into a house other than maybe just to stub through the wall of the building.

 

[AJRiddle]

The 4" is only because it connects to already existing 4" and would have needed some anyway. This was all formerly cast iron that some sections had been replaced by ABS & PVC by prior owners. Would have just done 3" if I didn't need a couple pieces of 4" anyway.

 

[Nagrom]

Looks good.

I am plumbing a similar bathroom and found this thread. Everyone says this is good but the UPC 2021 says that the wet vent needs to be 3" pipe to catch 6 fixture units (1 lav + 2 tub + 3 WC)

I'd love to use 2" because it'll be hard or impossible to fit 3", but I don't understand how it's legal?

 

[wwhitney]

I am plumbing a similar bathroom and found this thread. Everyone says this is good but the UPC 2021 says that the wet vent needs to be 3" pipe to catch 6 fixture units (1 lav + 2 tub + 3 WC)

Wet vent sizing is based on the units of drainage being carried by the pipe that is acting as a wet vent. Up to 4, 2" is OK; above 4 you need 3".

The first segment of wet vent is between the lav and the tub. This segment is carrying only 1 DFU of drainage, the lav. So 2" is OK. The second segment of wet vent is between the tub and the WC. This segment is carrying 3 DFUs of drainage, the lav and the tub. So 2" is OK.

After the WC joins, it is no longer a wet vent.

Cheers, Wayne