Bathroom DWV layout sanity check

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DanFL

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I'm looking for a sanity check on this bathroom layout (Florida Building Code / IPC). Two questions:

1. Is the general layout OK? I'm angling the 2" shower drain over to the right to get the vent lined up in the wall that will be added later.

bathroom_2_layout.jpg


2. The existing 3" main drain I need to tie into is inconveniently located 1.5" too far to the right. To get the toilet centered between the left/right walls, I need to shift it over to the center line (laser line in pic). Can I do this by adding 2 back-to-back 22.5 elbows, and rotate them slightly to get the centers aligned? This will create a slight drop in the line where those 2 elbows connect (i.e. more that 1/4" per foot) just at that connection. Is this allowed? Other suggestions? I'd prefer to avoid an offset flange if possible. I don't have any wiggle room in the placement of that future wall on the right.

3inch_drain_offset.jpg
 

wwhitney

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1) OK, as long as the trap arm, from the trap outlet to the vent wye, is sloped at least 1/4" per foot but falls no more than 2" overall.

It would be nice to use only a 45 between the horizontal 3x3x2 wye and the 2" vent wye. To that end, the vent wye could be moved somewhat to the left and rolled 45 degrees. Then it would use a 60 to turn vertical under the wall. [Or as you are under the IPC, you could switch to a san-tee on its back plus a 45 if it would make the difference. But all things being equal, a wye is better.]

2) What is the height difference from the top of the existing 3" building drain and the finish floor? If you have enough height, you can rotate your closet bend 22.5 or 45 degrees about the horizontal axis, and put a 22.5 or 45 degree elbow (possibly street) to turn to vertical under the closet flange.

Cheers, Wayne
 

DanFL

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Thanks Wayne.
1. I think what you are suggesting is this? Just curious, what's the advantage of rolling the 2" wye? Just keeping everything tighter together?
20210824_140416_small.jpg


2. I have just over 10" from top of drain to finished floor. I like your idea better and wasn't sure if I was allow to rotate a closet bend like that. My only concern is the offset of a 4" 22.5 elbow inserted in the rolled closet bend. I believe it will be greater than the 1.5" horizontal shift that I need. I don't have any 4" 22.5 fittings at the moment to confirm. Do they make an 4" 11.25 elbow (certainly haven't seen them at the box stores). On a side note, isn't there a handy table that tells you what the offsets are for the various PVC sizes and angled fittings?
 

wwhitney

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1) The only point is to get the vent wye farther to left, so that when you stick a street 45 into the end, the 45 outlet can point directly at the 3x3x2 wye branch inlet. If you can achieve that without rolling, that's fine; rolling just gives you another spatial option.

2) Per Charlotte's catalog, if you stick a 4" street 22.5 into a 4x3 hub x hub closet bend rolled 22.5 off vertical, then the slanted run is 3" + 2.75", and the vertical part of the street elbow is another 1" to the bottom of the hub. So the horizontal jog is sin(22.5)*5.75" = 2.2", and the vertical rise from center line is cos(22.5)*5.75" + 1" = 6.3". The outer radius of 3" pipe and the depth of a 4" hub are both 1.75", so that's also the rise from top of 3" horizontal line to top of elbow hub.

If you switch to a 3" quarter bend and a 3" street 22.5, then the slanted run is 3-1/16" + 2-5/16" = 5.375", so the horizontal offset is now sin(22.5)*5.375" = 2.05".

If you use a 3x4 hub x spigot closet bend, I think you can cut the spigot end down to 3.5" from center line and still fully seat a 4" hub (to be verified). In that case, with a 22.5 degree bend, the diagonal segment would 4.5", for a horizontal offset of sin(22.5) * 4.5" = 1.72".

If that's not close enough, then I don't see how to make my idea work, as 11.25 degree bends aren't made in 4" Schedule 40 DWV to my knowledge.

You definitely could use a 3" 45, a 3" street 45, and a 3" street 22.5 to achieve a 1.5" offset while turning from horizontal to vertical. The only question is if that would be too tall; I don't think it would be, but I haven't done the complicated trigonometry. Worst case you'd need a 3" spigot end closet end, I think.

To get back to your question in the OP, if you have room between the 3x3x2 wye and the closet bend, your original idea would work. You could use street 22.5 elbows to get a 1.2" horizontal offset. To get more, you'd need normal 22.5 elbows, which would put the horizontal offset at 1.76" at least. So then you could roll the offset about 30 degrees to get to 1.5". And the resulting vertical offset would be fine.

Cheers, Wayne
 

DanFL

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Wayne - thanks for that very detailed explanation. I will have to try these various fitting options to see which one will work best, but I think I've got a couple of good options now to move forward.
 

DanFL

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Here is a 3x4 hub x spigot with 4" 22.5 elbow. You were correct about being able to cut it down to 3.5" from the center line. That leaves 7/8" of the 4" part closet elbow inserted into the 22.5 hub and fully seated, with the end of the hub butting right up to the 3" section on the closet elbow. Is that acceptable/allowed to not have full contact with the 1.75" inside the hub? If so, I'll be happy with the 1.72" offset.

closet_elbow.JPG
 

wwhitney

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I would say that reducing the overlap of spigot and hub to only 7/8" is marginal and I'd choose another solution. (I was imagining the spigot end went all the way to the inside corner. BTW what is the total spigot length? Looks like 2-3/8"?)

I think I'd do 1.5" with worrying much about it, and 1.25" if the other solutions are not very good, but going down to 50% is not something I could advise.

Cheers, Wayne
 
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James Henry

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Glue a street 3x2 wye into the two 1/8th bends you have for the offset, then glue a street 3x4 closet bend or 90 or sweep into the end of the 3x2 wye. dig back under the concrete and cut the drain at the exact point where when you glue everything together the toilet flange is centered 12" from the finish wall.
If theirs a foundation back there then forget it.
 
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