Wet Venting possible with raised fixture on horizontal branch?

Users who are viewing this thread

Manuel

New Member
Messages
3
Reaction score
0
Points
1
Location
Hawaii
So I've got a section of a level here and it shows what I currently have modeled out for this bathroom. Is wet venting in this fashion possible, where the fixture is branching off vertically or rolled @ 45 degrees from the main branch pipe acting as a wet vent? From what I can tell in the UPC, fixtures on the same level should be horizontally connected to the branch line so this shouldn't be viable but I wanted to make double sure by asking.

The reason I have it like this in the first place is that the slab joists below are keeping me from raising the main branch from coming any closer to the finished floor and I'm already pushing the 2' max drain head to p trap on those floor fixtures due to the raised floor.
 

Attachments

  • PXL_20210923_175833493.MP_3.jpg
    PXL_20210923_175833493.MP_3.jpg
    65.4 KB · Views: 90

wwhitney

Well-Known Member
Messages
5,051
Reaction score
1,263
Points
113
Location
Berkeley, CA
No, that doesn't work. It violates the trap weir rule, the trap arm needs to be vented before it falls more than one pipe diameter from the trap elbow outlet.

If the bottom of the slab joists is more than 24" from the finished floor I don't have a solution for you. Unless you have room in the raised deck sleepers to run a 2" drain across, rerouting the lav drain to run towards the tub and shower, and can fit the traps above the slab.

Cheers, Wayne
 

Tuttles Revenge

In the Trades
Messages
2,472
Reaction score
748
Points
113
There's nothing there that prevents a horizontal wet vented system from working as long as the standpipe to the trap isn't too long. You still need trap arm lengths that meet code like any horizontal system.

The drawing being out of perspective is making it difficult to understand your intentions. A plan view/Top Down drawing of the layout of the bathroom that also shows the direction of the beams might help. Something simple.
 

wwhitney

Well-Known Member
Messages
5,051
Reaction score
1,263
Points
113
Location
Berkeley, CA
Theres nothing there that prevents a horizontal wet vented system from working as long as the standpipe to the trap isn't too long.
As I understand it, the OP's drawing is a true section, and the floor framing is more than 24" tall.

So the problem is that with the horizontal branch drain below the floor framing, it's not possible to comply with the two different constraints on the trap elevation. On the one hand, it has to be at most one pipe diameter above the horizontal branch drain for horizontal wet venting. On the other hand, the tailpiece from the drain to the trap is limited to 24".

Cheers, Wayne
 

Tuttles Revenge

In the Trades
Messages
2,472
Reaction score
748
Points
113
OK.. I read that again and see that. That was between my first and third cup of coffee ;)

So it could be done with horizontal wet venting if the standpipes were'nt too tall. Reading my illustrated manual with explanations as to the Why.. they explain that the tail piece length rule has 2 parts.
1- to prevent odor from material built up in an excessively long tail piece (meh)
2- that an excessively long tail piece could create velocities that could siphon a trap despite it being vented.

Personally I would ask the inspector for a variance if you were on the cusp of that distance and install it like a true horizontal wet vent with the entire system on the 1/4" slope to maintain that venting.
 

wwhitney

Well-Known Member
Messages
5,051
Reaction score
1,263
Points
113
Location
Berkeley, CA
Looking at Hawaii's UPC, they've amended it to allow AAVs. https://up.codes/viewer/hawaii/upc-2018/chapter/9/vents#new_912.0 So an AAV could be put inside the joist bay, if vented access can be provided without violating whatever floor to floor fire separation is required.

They also allowed combination waste and vent systems where "structural conditions preclude the installation of conventional systems." https://up.codes/viewer/hawaii/upc-2018/chapter/9/vents#910.0 The section on vertical waste pipes in a combination waste and vent allows a horizontal branch at a 45 degree angle.

Cheers, Wayne
 

Reach4

Well-Known Member
Messages
34,540
Reaction score
3,496
Points
113
Location
IL
The reason I have it like this in the first place is that the slab joists below are keeping me from raising the main branch from coming any closer to the finished floor and I'm already pushing the 2' max drain head to p trap on those floor fixtures due to the raised floor.
1. Can you drill through the joists?

2. Would the void be big enough to contain the horizontal wet vent/drain and trap arms? Let the U of each trap extend though subfloor holes between joists.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks