How to vent separate tub and shower after removing wall

[BuiltByAppelhans]

I need to redo the plumbing for a free standing tub and an adjacent shower. See the pictures below. This is a 90's build that previously hid a horizontal run in a half wall between built in tub and shower. I have a drop ceiling under the shower drain and an existing vent, but not under the bathtub drain until I get closer to the shower area. I plan to built a firred out wall to hold a new transition into the existing vent pipe to get around the LVL beam.

How do I set this up correctly without screwing up the venting? I figured out from reading the forums that I cannot run a horizontal vent section below the tub (below the overflow water line). I think I need to bring both the shower and the tub drain to the vent before sending pipe further downhill to the waste line? I'm not sure I can fit all the fittings right at the vent and still have enough drop to get into the existing waste line (see the pictures).

Any help? Do I have to bring both shower and tub to the vent in a 4 way fitting, or is there an easier way to do this?

 

[Jeff H Young]

looks wrong to begin with . move drain line to wall so vent can rise vertical

 

[Sponsor]

 

[Terry]

That looks strange. They had capped off the vent on the top of the double fixture fitting, then ran a line off the top of the tub waste and overflow, which did nothing for the venting. At least that's what it looks like to me.

You could run horizontal near the wall with the vent pointing up, picking up the shower on the way. The shower comes off of a wye or combo. After the vent, you would then pick up the tub.

How to bring the vent into the wall though? Is that supporting structure underneath? Is the solution perhaps making the wall thicker there to have a place for the vent to come up through?

 

[Jeff H Young]

looks pretty messed up to me too . but not clear, certainly wrong though

 

[BuiltByAppelhans]

That looks strange. They had capped off the vent on the top of the double fixture fitting, then ran a line off the top of the tub waste and overflow, which did nothing for the venting. At least that's what it looks like to me.

You could run horizontal near the wall with the vent pointing up, picking up the shower on the way. The shower comes off of a wye or combo. After the vent, you would then pick up the tub.

How to bring the vent into the wall though? Is that supporting structure underneath? Is the solution perhaps making the wall thicker there to have a place for the vent to come up through?

All the old stuff was junk and done wrong by some previous tile guys. They removed the original tub and only had a shower, which they didn't vent correctly. So I'll cut all that junk out and start fresh.

I'll also build the wall out thicker to have a place for the vent to come through and avoid the structural member.

I made some drawings. Terry, I think you are describing option #2? Can I bring the tub to intercept the shower after the shower hits the vent and takes off for the drain? Is this a wet vent?

 

[wwhitney]

Something like the drawing below strikes me as the obvious layout given the choices you show of tailpiece, vent, and branch drain locations. Blue can be 1.5", red is 2". Dry vent the bathtub, use it to wet vent the shower. The first short segment at the tub drain is the trap u-bend, the elbow outlet points towards the wall with the vent.

The vent connection on the bathtub fixture drain is taken off the horizontal via a wye, combo or san-tee on its back (less preferred, but useful if space is tight). The fitting is rolled to be 45 degrees above horizontal (half-way to vertical) so that the vent starts off rising and continues rising until it hits a 45 or 60 (if you use a wye) to turn vertical at the marked location).

Cheers, Wayne

 

[BuiltByAppelhans]

Something like the drawing below strikes me as the obvious layout given the choices you show of tailpiece, vent, and branch drain locations. Blue can be 1.5", red is 2". Dry vent the bathtub, use it to wet vent the shower. The first short segment at the tub drain is the trap u-bend, the elbow outlet points towards the wall with the vent.

The vent connection on the bathtub fixture drain is taken off the horizontal via a wye, combo or san-tee on its back (less preferred, but useful if space is tight). The fitting is rolled to be 45 degrees above horizontal (half-way to vertical) so that the vent starts off rising and continues rising until it hits a 45 or 60 (if you use a wye) to turn vertical at the marked location).

Cheers, Wayne

View attachment 82234

Thanks Wayne--I thought I read somewhere that a wet vent has to be 2" not 1.5"? I could make the wet vent leg from the vent to the shower 2" if so.

Also, could I use long sweep 90s instead of the 45s you showed from the bathtub? This would let me start making the turns in the drop ceiling where I would not have to drill any joists.

 

[wwhitney]

Thanks Wayne--I thought I read somewhere that a wet vent has to be 2" not 1.5"? I could make the wet vent leg from the vent to the shower 2" if so.

That's an IPC vs UPC difference. If you are in CO, it uses the IPC/IRC, not the UPC. But if it's not structurally inconvenient then you could use a 2" trap and trap arm on the tub, or just 2" from the vent takeoff downstream (which is actually a UPC requirement for any tub, wet venting or not).

Also, could I use long sweep 90s instead of the 45s you showed from the bathtub? This would let me start making the turns in the drop ceiling where I would not have to drill any joists.

Yes, you could, although I'm not following your description: I would think with a drop ceiling you could easily use the 45s, while if you were running through joists you'd need to use the LT90 to avoid having to drill joists at a 45.

Note than any trap arm (from the trap to the vent connection) may not fall more than one pipe diameter.

Cheers, Wayne

 

[Jeff H Young]

the short red section of shower waste needs to contnue 2 inch or larger you cant drain 2 inch into 1.5

 

[wwhitney]

the short red section of shower waste needs to contnue 2 inch or larger you cant drain 2 inch into 1.5

If you're referring to my drawing, there is no 2" draining into 1.5".

Cheers, Wayne

 

[Jeff H Young]

got the colors mixed up and assumed running 2 inch drain for the tub except trap arm . just so forieghn to me running 1 1/2 " drain lines we need a 2 inch drain here

 

[BuiltByAppelhans]

Regarding Wayne's picture, I can't see how I could get from the tub trap to the vent without drilling through a joist (which is ok with me so see my plan below). I don't see how I can have the tub trap located in a normal joist bay and ever get under those joists in the drop ceiling without violating the wyre rule. If the tub trap is in the normal ceiling I have to drill through a joist.

The drain stack and angle that it comes out is fixed, and it seems hard to get the shower to directly tie into it and use the tub as a wet vent. The fan vent piping is making the spaces pretty tight.

Would it be ok to just have the shower and tub head to the vent wall and meet at the same level with a sanitary cross tee like I show in the picture? Is there a better T I should use? I've read some advise on these forums about not using the double sanitary tee, but I think it mostly only applied to toilets? I think stacked santees would not allow me to drill through the center of both joists, and putting the shower santee at a level below the joists in the drop ceiling would make it difficult to get the drain leg threaded through the fan exhaust pipe.

 

[wwhitney]

Regarding Wayne's picture, I can't see how I could get from the tub trap to the vent without drilling through a joist (which is ok with me so see my plan below). I don't see how I can have the tub trap located in a normal joist bay and ever get under those joists in the drop ceiling without violating the weir rule. If the tub trap is in the normal ceiling I have to drill through a joist.

Ah, the short answer is that I didn't realize that some of the bathroom was over a drop ceiling, and some wasn't. Now that you've opened up more of the floor, the latest picture makes that clear.

What size are the joists? And can you repost that picture again without any markups? I take it the trap shows the desired tub trap location, and the shower drain is not moving much.

Would it be so difficult to change the fitting where the 2" drain turns down into the wall below, so that you can approach that location from a different angle with your new drain?

How are you going to get your vent over that beam while having it concealed? The vent will be below the flood rim level of the fixtures, so it has to rise at an angle of at least 45 degrees above horizontal. I.e. it can just kiss the corner of the beam (if the 2x4 is a just a nailer, notching it is fine), but can't turn horizontal.

Cheers, Wayne

 

[BuiltByAppelhans]

I'm going to build a new 2x4 wall on top of the insulated wall to give room for the vent to jog up, so no worries about that.

I can't access the fitting at the top of the drain where it turns down the wall. So I'm stuck with the existing drain angle, at least for a little section of pipe.

Yes, shower drain is pretty close to where it will be, and the tub drain is where I show the trap. Vent wall is not a problem, I'll cut the nailer and have a new 2x4 false wall on top of the nailer.

 

[BuiltByAppelhans]

Joists are 9.25 deep, 16" on center.

 

[wwhitney]

OK, so using a 2" double fixture fitting (the better version of the double san-tee you asked about) works and is probably the simplest thing to do. You can drill a 2.5" hole in a 2x10 for a 2" shower drain, as long as the hole is 2" clear from the top and bottom. Lining up the lower horizontal drain with the existing angle will be a bit tricky.

Below is a slightly goofy option that only drills the joist once. Red is 2"; blue can be 1.5" but 2" is OK. The idea here is with 2x10 joists 16" o.c., a 1.5" or 2" pipe that is perpendicular to the joists but 45 degrees off plumb should be able to pass under one joist while passing over another joist (beam in this case), if my sense of geometry is correct.

That is, the tub trap arm LT90s after going through the joist to end up at a location in the joist bay where a combo rolled 45 degrees off plumb for the vent takeoff will just kiss the beam top corner, then proceeds to a quarter bend with outlet also rolled 45 degrees off plumb to get under the joist. Next is a san-tee with the barrel also 45 degrees off plumb to receive the shower trap arm. Finally whatever collection of elbows (no quarter bends) you need to connect that to the existing lower horizontal drain; still tricky to get those angles right.

To avoid any angle trickiness, you could do the following instead, working backwards from the lower horizontal drain: LT90 to go vertical; street san-tee for the shower trap arm; street quarter bend to point perpendicular to the joist towards the vent wall. [I think that's as low as you can get while having the vertical segment; if that's too low you can change one of the street connections to have a short section of pipe.] Then through the joist to a LT90 to turn parallel to the beam, and upstream of that is as in the drawing below. Not sure if two LT90s on the tub trap arm and zero on the shower drain is any better or worse than the one LT90 on each trap arm you'd have with the double fixture fitting.

So a few different options. If opening the wall below is an option, you could adjust the angle of the lower horizontal drain which might simplify the work above.

Cheers, Wayne

 

[BuiltByAppelhans]

Wayne, I think I understand your ideas. Does the circled purple section have to be exactly 45 degrees from plumb? I could imagine just connecting the current drain output and the drain LT90 near the beam with maybe a 1/8 turn near the drain and LT90 at the beam. There would be a santee in between to pick up the shower trap arm.

Is there something about 45 degrees for the wet vent? I don't think I need the 45 degrees to slide under the middle joist, because the plumbing against the exterior wall can be lower than the top of joist level--I'll just be going straight vertical through a secondary wall I will build, and then a small jog in the vent to get into the real exterior wall.

 

[wwhitney]

Well, 45 degrees is the boundary between horizontal and vertical. And there is an argument that in horizontal wet venting the wet vent should stay horizontal, even though, for example, the definition of horizontal branch allows vertical segments.

So I picked 45 degrees as the steepest horizontal option, to be sure to get under the joist. If you can get under the joist with less slope, that's fine, but the the shower drain fitting to wet vent fitting would need to be a combo instead of a san-tee. As the san-tee can only be used if its outlet is vertical, meaning at least 45 degrees above horizontal.

The tricky part either way will be the bend at the bottom to connect to the existing. You can hold a piece of pipe at the correct slanted angle running into the existing pipe and try to measure the acute angle on the upper left (in the picture). If it's close to 45 degrees or 22.5 degrees you can try doing it with one elbow, but most likely it will need two elbows. (2) 22.5 degree elbows if the angle is between 22.5 and 45; or a 22.5 degree and a 45 degree elbow if the angle is between 45 and 67.5 degrees. Then you'll have to rotate the elbow-elbow joint until you get the correct angle, and you'll also get an out of plane offset that affect where you the new pipe or cut the existing pipe.

BTW, I don't necessarily think that this option is better than the double fixture fitting option or the vertical segment option. The only real upside to it is one less hole in the joist, which is probably not worth a lot extra trouble. The vertical segment option would be the easiest to do, as long as the available height is sufficient.

Cheers, Wayne

 

[BuiltByAppelhans]

It is kinda worth a lot of trouble to avoid drilling the joist, because I will be attaching nailers to each side of the joist to drop the subfloor for a curbless shower, and having to work these nailers around hole is kinda a pain. I think the current drain pipe is angled exactly 22.5 or 45 from perpendicular to the joists. I think the angle from plumb that the wet vent would run is about 30 degrees, so less than vertical.

I don't think there is room for the vertical option you suggested.

Can I just use a vent tee where I connect the tub arm to the vent near the beam? It seems like you are showing a combo.

 

[wwhitney]

I recommend a combo if it fits. I guess the question would be whether the combo branch would still be curving as it breaks through the subfloor, and if so whether that would be a problem for your framing. If a combo doesn't fit, the IPC/IRC allows a san-tee on its back. The fitting needs to be rolled up at least 45 degrees above horizontal.

Vent tees are only used when all the connections are vents, although I'd be hard pressed to articulate a way in which it would be worse than a san-tee on its back for this application. But is there any upside to a vent tee, versus a san-tee on its back?

Cheers, Wayne