Shower vent horizontal run

[TAPReactor]

I'd like to relocate a vent that's currently serving a tub and shower. It's embedded in a shower wall that I'd like to replace with a glass panel. Here's the current configuration:

Since I'm up against an exterior wall, I was thinking of relocating the vent under the shower to wall (B). This requires a 4' 6" 'horizontal' run as in the following:

It seems to me that if I get the vent in behind the shower and tub tie in to the main drain line then this should provide the necessary air to push it along. Any issues you can spot with this configuration and the 'horizontal' run?

 

[TAPReactor]

After sleeping on it I can see the horizontal run below the flood rim is going to be a problem. Thus, Plan #2 runs the main drain to the exterior wall and turns up for a distance to exceed the flood rim, then turns horizontal and runs through the wall and around the corner to meet the vertical vent leading to the roof. A lot more work but probably a better result.

2nd, 3rd and 4th opinions would be welcomed!

-George

 

[Sponsor]

 

[wwhitney]

All the horizontal pipes have to be either active drains, or vents that are 6" above the flood rim level of the associated fixtures. Both of your drawings have flat vent takeoffs that are not allowed.

The horizontal pipe starting at the trap outlet (the trap arm) can not turn downward before being vented. It can fall at most 1 pipe diameter before being vented (the trap weir rule).

What's wrong with running a vent up the exterior wall? If that's possible, the simplest solution is to move the existing double san-tee to the corner at the exterior wall.

Another option would be to replace the existing wall with a short wall that's about 12" higher than the bathtub rim. That way the existing double san-tee can remain where it is, the vent can rise 6" above the bathtub rim, and then turn horizontal to get to the exterior wall.

Cheers, Wayne

P.S. On switching to a double fixture fitting, I don't recall if its required, but it's certainly non-negative.

 

[TAPReactor]

Wayne, thanks for the note. Originally I was trying to avoid the vent rise at the exterior wall due to a tight turn where the roof line falls but looking at it again it shouldn't be too difficult. I agree with your suggestion of placing the double san-tee at the corner of the exterior wall and bringing both trap arms to it. Thanks for the reminder not to turn the trap arm down before being vented. The new configuration would be something like this, let me know if you have any comments (the trap arms are approximate, hard to draw the perspective but they meet the sanitary tee at the wall, I'll have to jog the main line over a bit to avoid a roof truss where the vent enters the attic):

This may work, if not I'll explore the knee wall option but then I suppose I'll have to cut my shower glass which isn't the end of the world.

Thanks,

George

 

[Reach4]

You could wet vent the shower with the tub.

 

[wwhitney]

Or vice versa.

You also have the option to jog the vent in the wall. If 2x4 construction, you'd be limited to jogging two stud bays, and you'd have to double the studs. Or use stud shoes, which are a good idea anyway.

Cheers, Wayne

 

[Reach4]

Or vice versa.

What fittings would you envision where the vent joins the trap arm and the drainage makes the turn?

 

[wwhitney]

What fittings would you envision where the vent joins the trap arm and the drainage makes the turn?

It seems to me the geometry is basically equivalent, whether the dry vent comes off the shower fixture drain or the bathtub fixture drain.

If there's the available height for a san-tee with a street LT90 on its outlet, then the two trap arms are at different elevations. One hits the san-tee side inlet, and the other hits the drain after the LT90 with a wye (or combo).

If there's not available height, then one of the trap arms needs to run under (or near and parallel to) the exterior wall, then an upright combo for the vent take off (or wye plus 60 if running next to the wall), then a LT90 to turn towards the drain at the bottom of the picture, and then the other trap arm joins the drain with a wye (or combo).

Cheers, Wayne

 

[Reach4]

If there's not available height, then one of the trap arms needs to run under (or near and parallel to) the exterior wall, then an upright combo for the vent take off (or wye plus 60 if running next to the wall), then a LT90 to turn towards the drain at the bottom of the picture, and then the other trap arm joins the drain with a wye (or combo).

So for minimum height, 3 fittings with a combo. or even a santee on its back, in the middle for the dry vent connection. I was thinking maybe some *-heel fitting could cut that to two. Those are harder to buy anyway.

 

[wwhitney]

So for minimum height, 3 fittings with a combo. or even a santee on its back, in the middle for the dry vent connection. I was thinking maybe some *-heel fitting could cut that to two. Those are harder to buy anyway.

Idaho plumbing code seems to be based on the UPC, so no santee on its back, or side inlet bends for venting. Also, all those side inlet fittings seem to only be available in 3" and larger (at least from Charlotte).

But that does mean there is an allowance for the vent to turn horizontal below the height 6" above the flood rim, where a vertical rise is "prohibited by structural conditions." Putting the san-tee where the vent can rise sufficiently is a better solution, but if that is not feasible, going horizontal below the floor is an option.

http://epubs.iapmo.org/2017/Idaho/

Cheers, Wayne

 

[Reach4]

Idaho plumbing code seems to be based on the UPC, so no santee on its back, or side inlet bends for venting. Also, all those side inlet fittings seem to only be available in 3" and larger.

Ahh. I had thought it was IPC. So combo or wye. ( maybe 2x2x1.5 I am thinking)

So with UPC, that horizontal dry venting becomes possible, but that takes some height too.

 

[TAPReactor]

Great! I believe this sketch incorporates your suggestions: