Moving a tub--will this vent properly?

[Chesterton]

I am renovating my master bathroom and changing the location of the tub. It was originally located where the sink is in the drawing below. The sink will now use that 1.5" line (I didn't even know you could use a 1.5" with a tub?). The new location of the tub is shown below. My concern is that this location will place two fixtures above the vent and I believe there is only supposed to be one. If necessary I could run the tub drain parallel to the main 3" waste drain and join after the vent. What are your thoughts? Flow is left to right.

 

[wwhitney]

- Your horizontal vent section will need to be at least 6" above all the fixture flood rims.
- Your sink trap arm can't drop down like that before the vent. Run it across horizontal (1/4" per foot slope) to a san-tee at the vent/drain.
- The middle vent riser is superfluous, but if it's already there, no need to remove it.
- IPC does allow the tub and shower trap arms to combine before they reach a common vent. But having the tub parallel the shower drain and only join after the vent comes off would be more typical.
- The drains upstream of the WC can be 2".
- Not sure on cleanout requirements.

Cheers, Wayne

 

[Sponsor]

 

[wwhitney]

Oh, one more important point. While the IPC does not require it, the IRC's plumbing section P3108.1 requires that on a horizontal wet vent each fixture connect horizontally to the wet vent. And it appears that Pennsylvania has adopted the plumbing sections of the IRC, rather than just the IPC, without providing the option to use the IPC instead.

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So, you can't join the WC to the top of the horizontal wet vent as shown. Your options all require more width in the joist bay (if this is in a framed floor) than your drawing would:

1) Put a horizontal wye in the 3" horizontal wet vent, and connect the WC to the branch inlet of the wye with a closet bend.
2) Use the middle vent riser in your diagram to dry vent the WC. To do this you'd need to keep the tub and shower separate from and parallel to the WC drain, and only join them into 3" line downstream of the middle vent riser takeoff.

Cheers, Wayne

 

[Chesterton]

- Your horizontal vent section will need to be at least 6" above all the fixture flood rims.
- Your sink trap arm can't drop down like that before the vent. Run it across horizontal (1/4" per foot slope) to a san-tee at the vent/drain.
- The middle vent riser is superfluous, but if it's already there, no need to remove it.
- IPC does allow the tub and shower trap arms to combine before they reach a common vent. But having the tub parallel the shower drain and only join after the vent comes off would be more typical.
- The drains upstream of the WC can be 2".
- Not sure on cleanout requirements.

Cheers, Wayne

Thanks! Revised below. I've converted the superfluous middle riser to be the sink drain, which now has a san-tee. I've capped the final vent riser. And although not shown in the drawing, it sounds like the "advanced move" would be to run the tub drain a foot or so extra and join after the vent. Again, thanks for the help!

 

[Chesterton]

Oh, one more important point. While the IPC does not require it, the IRC's plumbing section P3108.1 requires that on a horizontal wet vent each fixture connect horizontally to the wet vent. And it appears that Pennsylvania has adopted the plumbing sections of the IRC, rather than just the IPC, without providing the option to use the IPC instead.

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Explore a searchable database of US construction and building code. Code regulations are consolidated by state and city for easier navigation.

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So, you can't join the WC to the top of the horizontal wet vent as shown. Your options all require more width in the joist bay (if this is in a framed floor) than your drawing would:

1) Put a horizontal wye in the 3" horizontal wet vent, and connect the WC to the branch inlet of the wye with a closet bend.
2) Use the middle vent riser in your diagram to dry vent the WC. To do this you'd need to keep the tub and shower separate from and parallel to the WC drain, and only join them into 3" line downstream of the middle vent riser takeoff.

Cheers, Wayne

Stink. I already updated my drawing
Yes, you are correct--this is in a finished joist bay. Before I make my new drawing I want to make sure I understand: Even though there is currently a closet bend vertically to the wet vent, it would be more awesome to closet bend to a horizontal wye. Also, there's a wall there so I can put dry vents basically anywhere after I make the runs from the tub and shower. So I could even vent those before I connect to the wet vent. At any rate, the new order will be:

dry vent -> horizontal wye with closet bend to wc -> dry vent -> horizontal wye with connects to tub and shower -> 1.5" wet vent for sink.

Does that sound right?

 

[wwhitney]

Stink. I already updated my drawing

Yeah, sorry, that issue occurred to me after my first post.

I didn't follow the rest of your post, sorry. The issue with your second drawing is that you have the closet flange going directly into an upright combo on the 3" horizontal drain. So the WC is connecting vertically to the horizontal wet vent, not horizontally.

If you make a new drawing, I think a floor plan would be better than an elevation, and that would let you show the walls in which you have or could have dry vents.

Cheers, Wayne

 

[Chesterton]

Dang. I super-duper want to keep the vertical connection from the WC to the 3" line.

Updated elevation below. I am not showing the sink because it's easy to vent and complicates things. And I'm not showing existing vents because I can put those all over the place.

So we have a tub, shower, and WC. I really don't want to have to add another connection to the existing Main because it's really hard to get to. That's my primary motivation for the vertical connection to the WC--that's where it already is so things are already in the right place. If I shift to the side, the consequences propagate. Thanks again--I really appreciate the guidance.

 

[wwhitney]

Dang. I super-duper want to keep the vertical connection from the WC to the 3" line.

There are probably some options to do that, you just need to change the connectivity from the simple drawing of your 2nd elevation.

Please add the lav to the floor plan, as it can be used to wet vent the WC, so where it is located bears on this issue.

Also, I infer your joist bays run left-right on the page. Is there room in the joist bay with the existing 3" to add a parallel 2" either above (on the page) or below (on the page) the 3" line? [Edit: a 3x3x2 wye plus a 2" street 45 with both inlets parallel puts the inlets 5" c-t-c. So you'd need 4-1/2"+ clear on either side of the 3" line.]

Cheers, Wayne

 

[Chesterton]

There are probably some options to do that, you just need to change the connectivity from the simple drawing of your 2nd elevation.

Please add the lav to the floor plan, as it can be used to wet vent the WC, so where it is located bears on this issue.

Also, I infer your joist bays run left-right on the page. Is there room in the joist bay with the existing 3" to add a parallel 2" either above (on the page) or below (on the page) the 3" line? [Edit: a 3x3x2 wye plus a 2" street 45 with both inlets parallel puts the inlets 5" c-t-c. So you'd need 4-1/2"+ clear on either side of the 3" line.]

Cheers, Wayne

Yes, the joists run l-r on the page. The 3" line is the only thing in the joist bay (it's running right down the middle) so there's lots of room on either side. I added the lav, but walls and ceiling are exposed, so adding vents is easy.

 

[Chesterton]

OK. I think I understand what's going on. In my original drawing the shower and tub accessed the vent through the 3" line, which turned that into a "wet vent". I could vent the shower and tub in the wall, then join the 3" line above the WC.

 

[wwhitney]

Well, the way I would put it is that (other than common venting, where two trap arms join and then hit a dry vent for both) a fixture drain needs to be vented before (dry vent) or as (wet vent) it hits another drain, So in the 2nd elevation, the WC is wet vented immediately below the closet flange, and has to meet the horizontal wet vent rules at that location.

In the diagram below, red = 3", blue = 2", and green = 1.5". So if you insist that the 3" line has to start at the closet flange and just go straight to the right, you can do something like the diagram (as long as the lav is a single lav). The tub is dry vented in the wall (I show a 2" tub trap, which lets the tub trap arm fall up to 2" between the trap and the vent takeoff, which allows up to 8' length if you achieve a perfect 1/4" per foot of slope). Then the shower is wet vented by the tub. The lav is dry vented as normal, and then the lav wet vents the WC.

Cheers, Wayne

 

[Chesterton]

Amazing. Elegant. Thank yoU!

 

[Chesterton]

Well, the way I would put it is that (other than common venting, where two trap arms join and then hit a dry vent for both) a fixture drain needs to be vented before (dry vent) or as (wet vent) it hits another drain, So in the 2nd elevation, the WC is wet vented immediately below the closet flange, and has to meet the horizontal wet vent rules at that location.

In the diagram below, red = 3", blue = 2", and green = 1.5". So if you insist that the 3" line has to start at the closet flange and just go straight to the right, you can do something like the diagram (as long as the lav is a single lav). The tub is dry vented in the wall (I show a 2" tub trap, which lets the tub trap arm fall up to 2" between the trap and the vent takeoff, which allows up to 8' length if you achieve a perfect 1/4" per foot of slope). Then the shower is wet vented by the tub. The lav is dry vented as normal, and then the lav wet vents the WC.

Cheers, Wayne

One last quick question just to satisfy curiosity: When I tore everything apart I found that the tub was on a 1.5" line and vented through the 1.5" lav (they shared a 1.5" line to the 3" line). Is that allowed? I would have expected the combined drains to require 2".

 

[wwhitney]

Under the IPC, a lav is 1 Drainage Fixture Unit (DFU), a tub is 2 DFU, and a 1-1/2" horizontal branch can carry up to 3 DFU.

Cheers, Wayne

 

[Chesterton]

I'm back! I think that I figured out how to drain the tub to the south. If I do that, can I get rid of old lav vent that the WC was using? It sticks out into the floor a little because of how the walls on the two floors line up and I'd love to clean that up. See attached.

 

[wwhitney]

If the tub is draining towards the bottom of the page and is vented separately (a dry vent, presumably), then you can dry vent the shower as shown and use it to wet vent the WC. That lets the lav drain run however you'd like, as it is no longer wet venting anything.

On the shower drain, if the drain location will really be the same distance off the wall at the top of the page as the closet flange, then use the u-bend of the trap to offset it a bit more from the wall, along with possibly another 45 if necessary. That should save you one or two 45s.

Cheers, Wayne

 

[Chesterton]

If the tub is draining towards the bottom of the page and is vented separately (a dry vent, presumably), then you can dry vent the shower as shown and use it to wet vent the WC. That lets the lav drain run however you'd like, as it is no longer wet venting anything.

On the shower drain, if the drain location will really be the same distance off the wall at the top of the page as the closet flange, then use the u-bend of the trap to offset it a bit more from the wall, along with possible another 45 if necessary. That should save you one or two 45s.

Cheers, Wayne

Perfect. Great tip on the U-bend. Thanks!