Stumped (once again) on routing vents and boring joists

[157]

I'm slogging through getting the plumbing laid out in my bathroom reno, but am currently completely stuck on routing the vent for the shower/toilet.

Here's the general layout — the toilet wet vents off the shower drain, so I'm running a 2" vent (vents are in green). It goes up the wall and into the ceiling (above is a finished attic):

The issue is that the attic joists above are 2x6 (nominal 1.75 x 5.5) 16" oc. I need to get through two of them so I can get the vent over to where it can go up into the attic (and ultimately, through the roof).

The only options I've come up with so far are:

1. Cheat and run 1 1/2" vent instead of 2" (that gets me just barely to the boring minimums)
2. Add sistering material, but I haven't found any clear guidelines on what that would be. Glued/screwed 3/4 plywood on both sides? 2 x 6 lengths glued/screwed?

Any other ideas?

 

[James Henry]

If you're under the IPC you only need 1-1/2" You have two 1-1/2" vertical vents, that's more than enough if your going to extend the final vertical section out the roof with 2".

 

[Sponsor]

 

[157]

If you're under the IPC you only need 1-1/2"

I’m in New York State. Other than comparing line-by-line, is there a way to tell if the IPC applies here?

 

[James Henry]

I’m in New York State. Other than comparing line-by-line, is there a way to tell if the IPC applies here?

You can Google what plumbing code you are under for your city and state. If you are under the IPC between 2015 and 2020 then the code states, "The dry vent serving a wet vent for a bathroom group shall be half the diameter of the largest drain served but no less than 1-1/4".

 

[157]

You can Google what plumbing code you are under for your city and state. If you are under the IPC between 2015 and 2020 then the code states, "The dry vent serving a wet vent for a bathroom group shall be half the diameter of the largest drain served but no less than 1-1/4".

Best I can find so far is legislation related to plumbing licensing:

“Workmanship must be of such character as to fully secure the results sought and as required in the New York State Uniform Fire Prevention and Building Code applicable to plumbing.”

[EDIT]
Just found this under General Legislation for Plumbing:
“Standards applicable to plumbing; compliance required.
A. New York State Uniform Fire Prevention and Building Code applicable to plumbing. All plumbing and drainage conditions and constructions shall comply with the provisions of the New York State Uniform Fire Prevention and Building Code applicable to plumbing and all other provisions of this Code applicable thereto.”

Sounds like it inherits New York State code?

 

[James Henry]

https://up.codes/viewer/new_york/ny-plumbing-code-2020/chapter/9/vents#906

Section, 912.3 Size.

 

[James Henry]

1-1/2" vent will serve 10 DFU,s. Section 906.1

 

[James Henry]

You have two 1-1/2" vertical vents, that's more than enough if your going to extend the final vertical section out the roof with 2".

 

[157]

You have two 1-1/2" vertical vents, that's more than enough if your going to extend the final vertical section out the roof with 2".

Awesome. And yes, one thing I do know is that I need to go through the roof at 3” to accommodate for frost, but that will be relatively easy since I can make that size step-up in the attic.

Thank you, James.

 

[wwhitney]

You ceiling joists are 5.5" tall, so your maximum hole diameter is 1.83". Further, your holes have to be at least 2" from the top and bottom edge, so your maximum hole diameter is 1.5". You can't run any vents through the ceiling joists (well, you could run a 1-1/4" copper DWV, but that's not sufficient for your toilet.)

https://up.codes/viewer/new_york/irc-2018/chapter/5/floors#R502.8.1

Cheers, Wayne

 

[157]

You ceiling joists are 5.5" tall, so your maximum hole diameter is 1.83". Further, your holes have to be at least 2" from the top and bottom edge, so your maximum hole diameter is 1.5". You can't run any vents through the ceiling joists (well, you could run a 1-1/4" copper DWV, but that's not sufficient for your toilet.)

https://up.codes/viewer/new_york/irc-2018/chapter/5/floors#R502.8.1

Cheers, Wayne

Yeah, I think I will end up running 1 1/2 and adding some sistered joists. Not ideal, but likely the best option.

The only other option is to wye off the shower drain further upstream, go through a joist, into the next joist bay and then run up into the ceiling. However, I think that conflicts with wet vent restrictions given the distance away from the toilet?

 

[wwhitney]

You combo at the WC is backwards.

How about dropping the ceiling 2" and running the vent under the joists?

Your last drawing is a plausible direction to go in. No problems on wet vent limits, but the vent takeoff is supposed to stay at an angle of at least 45 above horizontal until you reach 6" above the fixture flood rim.

So you'd be best off pointing the trap u-bend to the right on the page, then the trap elbow outlet up on the page (or at azimuth 22.5, to hit a 22.5 elbow if you need to get closer to the wall), then take off a vent with a wye rolled up 45 above horizontal that can rise into the wall without leaving the framing, then the shower drain can hit a long turn 90 and go left on the page to hit the WC drain.

Cheers, Wayne

 

[157]

You combo at the WC is backwards.

How about dropping the ceiling 2" and running the vent under the joists?

Your last drawing is a plausible direction to go in. No problems on wet vent limits, but the vent takeoff is supposed to stay at an angle of at least 45 above horizontal until you reach 6" above the fixture flood rim.

So you'd be best off pointing the trap u-bend to the right on the page, then the trap elbow outlet up on the page (or at azimuth 22.5, to hit a 22.5 elbow if you need to get closer to the wall), then take off a vent with a wye rolled up 45 above horizontal that can rise into the wall without leaving the framing, then the shower drain can hit a long turn 90 and go left on the page to hit the WC drain.

Cheers, Wayne

Still trying to parse this.... but what if there was an inline wye (rolled up 45 like you mentioned) with the vent taking off through the floor joist, over into the next joist bay, then up into the wall, and into the target ceiling joist bay?

 

[wwhitney]

Below is the idea I was trying to describe (new drain route in purple, new vent riser in green, vent in the ceiling joists not shown. The vent is not supposed to go horizontal at less than 6" above the flood rim level of the shower, and you don't want the vent pipe sticking out of the floor. [The purple right angle at the shower is just what you get from the two part p-trap.]

Aren't you going to have the same problem with the lav vent and the ceiling joists? Or are you going to use 1-1/4" copper DWV for that?

Cheers, Wayne

 

[157]

The vent is not supposed to go horizontal at less than 6" above the flood rim level of the shower, and you don't want the vent pipe sticking out of the floor. View attachment 69574

ok. This is slowly getting through to me. If I was to reinterpret this, it would be that the vent needs to immediately go vertical — i.e. once it has wye-ed off the drain line, it cannot be horizontal until it’s above the flood plain?

Aren't you going to have the same problem with the lav vent and the ceiling joists? Or are you going to use 1-1/4" copper DWV for that?
View attachment 69574

By chance (can’t take credit it is as-designed), the attic above that side of the room is behind a unfinished knee wall where it can first run directly up into the attic and then run over to hook into the vent going through the roof.

 

[wwhitney]

ok. This is slowly getting through to me. If I was to reinterpret this, it would be that the vent needs to immediately go vertical — i.e. once it has wye-ed off the drain line, it cannot be horizontal until it’s above the flood plain?

It has to take off vertical, and stay vertical, until 6" above the flood rim level of the associated fixture. No horizontal portions below the altitude defined as 6" above the flood rim level. And horizontal means more than 45 degrees from plumb; vertical means 45 degrees or less from plumb.

[This is not quite true at the fitting where you take off the vent, which has to be a wye (or combo). Requiring the wye side inlet to be at most 45 degrees from plumb would require the wye to be completely vertical. You can have the wye rolled up to 45 degrees or so off vertical, and a short pipe segment before hitting another elbow. Then the outlet of that elbow has to be at most 45 degrees off plumb. If you use a single fitting combo (wye plus 45), that all happens automatically.]

Cheers, Wayne

 

[157]

It has to take off vertical, and stay vertical, until 6" above the flood rim level of the associated fixture. No horizontal portions below the altitude defined as 6" above the flood rim level. And horizontal means more than 45 degrees from plumb; vertical means 45 degrees or less from plumb.

[This is not quite true at the fitting where you take off the vent, which has to be a wye (or combo). Requiring the wye side inlet to be at most 45 degrees from plumb would require the wye to be completely vertical. You can have the wye rolled up to 45 degrees or so off vertical, and a short pipe segment before hitting another elbow. Then the outlet of that elbow has to be at most 45 degrees off plumb. If you use a single fitting combo (wye plus 45), that all happens automatically.]

Cheers, Wayne

Got it. I think the trickiest part of this approach is getting the turn correct off the shower drain, but I think I can visualize the fittings: The trap can point towards that back wall (where the vent is going to run up) and then a long-sweep 90 would point it through the first joist (or, you made it sound like I could skip the 90 and just "turn" the trap outlet to point in the right direction?), a tilted wye would send off the vent, then another long-sweep 90 would send it off towards picking up the 3” toilet drain. Not sure how to connect into the 3” though.... it would be connecting into the 45+45 bend area. Maybe use a 3" wye like this and reduce down to 2" at one end?

 

[wwhitney]

Got it. I think the trickiest part of this approach is getting the turn correct off the shower drain, but I think I can visualize the fittings: The trap can point towards that back wall (where the vent is going to run up) and then a long-sweep 90 would point it through the first joist (or, you made it sound like I could skip the 90 and just "turn" the trap outlet to point in the right direction?)

Yeah, avoid an immediate long turn 90. A trap has an internal degree of freedom (in addition to the rotation around the inlet pipe). So if the U-bend (bottom half) points towards the back wall, then the elbow portion (top half of trap) can point 90 degrees to that. Assuming that gets you close enough to the wall for a wye rolled up 45 degrees to give a vent takeoff that stays within the framing as it goes from the floor system into the wall.

If it doesn't, turn the elbow portion of the trap only 67.5 degrees out of in-plane with the U-bend, then put in a flat 22.5 degree bend once you are close enough to the wall, then proceed with the vent takeoff.

Not sure how to connect into the 3” though.... it would be connecting into the 45+45 bend area. Maybe use a 3" wye like this and reduce down to 2" at one end?

Yes, precisely, use a 3" combo and a 3" x 2" reducer or bushing.

Cheers, Wayne

 

[157]

Yeah, avoid an immediate long turn 90. A trap has an internal degree of freedom (in addition to the rotation around the inlet pipe). So if the U-bend (bottom half) points towards the back wall, then the elbow portion (top half of trap) can point 90 degrees to that. Assuming that gets you close enough to the wall for a wye rolled up 45 degrees to give a vent takeoff that stays within the framing as it goes from the floor system into the wall.

If it doesn't, turn the elbow portion of the trap only 67.5 degrees out of in-plane with the U-bend, then put in a flat 22.5 degree bend once you are close enough to the wall, then proceed with the vent takeoff.

Cheers, Wayne

ok. I think the problem I’ll have is less about the distance to the wall (wall to center of drain is 10”), but more that the drain is pretty tight up against the joist, so it will limit how much I can turn that way. I may end up having to point the “wrong” direction— just to give myself some room to sweep around and get straightened out before I head through the joist.

 

[157]

So here's pictures of a mockup to illustrate what I mean...

The trap is pretty much exactly where it needs to be (minus the elevation), so one can see how the angles will be tricky to push the drain over to be under the wall. This mockup would require a nasty angled bore hole through that joist, so no good there...