Bathroom wet venting design feedback

[Wyeast]

Looking for some feedback on a bathroom drain system that I am knee deep in ->

I am building a large detached garage in Washington state with an upstairs living area which includes a bathroom (lavatory, toilet and shower). After many hours of reading this forum and the UPC, I've ran through many different options to approach the drainage system for the bathroom. The most relevant diagram I've found is the middle one below:

Screen Shot 2019-08-19 at 9.15.20 PM

Here is the bathroom configuration shown on our plans:

Garage Plans 2d

The bathroom is enclosed by a gable roof and sits on top of 3/4" subfloor and 11 7/8" TJI joists. I originally wanted to install the drain components through the TJI's, but have admitted defeat on that as all the pipes would be running perpendicular to the joists and I think it would get a bit to extreme with the amount of couplers and holes drilled through the joists. So I am looking to suspend the drain lines below the TJI's as they flow from the shower on the right -> toilet -> lavatory-> out to drain stack on the west (left side of drawings).

Here is a 3d drawing I've been using to lay the system out:

Garage plumbing diagrm 2

I am hoping to use a single 2" vent for this bathroom group that runs up through the roof on the east side of the gable (drawings are shown with typical north at the top). The shower is far enough away from the main wet-vent at the lavatory that I believe I would need the additional mid-length vent on the shower drain.

The toilet can connect down stream of the wet-vent attached to the lavatory and be within 6' per table 1002.2.

As for the combo wye that connects the lavatory wet-vent and shower to the main line I am unsure if it is acceptable to roll it up at an angle so that the lavatory drain connections can tuck away into the north wall?

As it stands I guess my questions prior to going out there and drilling holes through everything are:

1 - Is it acceptable to have that vent between the shower drain and wet-vent connection in order to not violate the trap arm length rules?

2 - Is it acceptable for the combo wye at the lavatory/wet-vent outlet to be rolled slightly off from vertical to allow the upstream pipes to tuck into the wall? I am thinking I could tilt it off vertical then come up into the wall with a 1/16th elbow.

3 - Related to cleanouts - I might not be reading section 707.4 of the UPC correctly, but it seems like it is saying that clean-outs are not required on installations above the ground floor (I.E the building drain) is that a correct interpretation?

"Excepting the building drain, its horizontal branches, and urinals, a cleanout shall not be required on a pipe
or piping that is above the floor level of the lowest floor of the building"



The reason I ask is I am finding it hard to keep the direction changes below 135 degrees on the shower drain while still having the shower drain centered in the pan. I currently have the toilet feeding into a combo which I could use to add a cleanout, but if not necessary I could just swap that for a simpler sweep 90.


I am happy to post pictures/videos or what ever is needed to better convey what I am trying to accomplish.

Hoping to get some honest feedback on what I have drawn as this is my first go at this, and I imagine I could be doing some aspect of it more efficiently.

Any help / comments are appreciated.

 

[wwhitney]

A couple quick comments:

1) The total vent area through the roof has to match at least the minimum building drain size [UPC 904.1]. So you'll need a 3" vent (or (2) 2" vents and a 1.5" vent) because you have a toilet that requires a 3" drain.

At which point you could just individually vent everything, with a 2" vent for the shower, a 2" vent for the toilet, and a 1.5" vent for the lavatory. Then you could eliminate your parallel drain runs to get the toilet connected as the downstream-most fixture. The vents could each penetrate the roof individually, or you could, I believe, combine them in the attic into a single 3" vent penetration.

2) As for getting the drain pipes into the TJIs, can't you just drill the exterior-most TJI and then slide them in from the outside?

Cheers, Wayne

 

[Sponsor]

 

[Wyeast]

Thanks for the reply.

I've got a 3" vent near the main stack down to the building drain, which combined with the other 2" vent serving the main bathroom fixtures should satisfy UPC 904.1.

Per your advice I took another stab at running all the drains along one main line - shown in the updated drawing below.



With this approach I believe I should be able to drill a single 3" "path" through the joists and outer wall which would allow me to install the system in the joists without using couplers every 16".

Here is another view of what I've got:

Garage - 2 - 1


I also spoke with the inspector this morning and confirmed that cleanouts are NOT required above the first floor in my situation per UPC 707.4 Exception (3).

Anyone see any glaring issues with what I have drawn here?