New bathrooms, abandoning old underslab, etc.

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Jeff H Young

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If I wasn't governed by plumbing codes I would model my work on a hybrid of UPC and IPC, leaning toward UPC . Certain things ingrained over 30 plus year in trade are hard to break. Why in world run a 2 inch vent on a w/c? because I've never run an 1-1/2 in my life! I've caught a few on tract homes plumbed by others and ignored seeing it.
So If I had no code though I'd adopt a few changes . And being your own home nothing wrong with better than meeting bare minimums.
 

Mikha'el

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OK, here's an option for you.

I'm pretty happy with it, except that wet venting the shower in the lower left seems hard or impossible to do in a reasonable manner, so I'm showing a dry vent for it (the circle). That could be a san-tee with a drop in drain elevation before the drain turns horizontal again, or it could be a horizontal take off (in which case it wouldn't be right at the corner). It could also be in a different wall of the shower.
View attachment 69441
Getting back to this little exercise... ground floor guest bath is figured out, slab demo done.

Re: that 2nd floor shower - just couldn't make it work on a wet vent, so I'm turning the trap arm to the outside wall, 1 1/2" vent up, 2" drain over to the 3" soil stack.
Is it ok to use this fitting at the top of the stack to tie in the shower? Does it need to be the long sweep version?

Thanks again...
 

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wwhitney

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A drain turning from horizontal to vertical just needs to be a regular quarter bend, not a long turn 90.

But the same applies to the side inlet as well, and I think you'll find that those parts you mentioned have no bend at all to the side inlet. So that means you can't use the side inlet for a drain connection. That's why I drew the drains joining on the horizontal before they hit the stack.

Cheers, Wayne
 

Mikha'el

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But the same applies to the side inlet as well, and I think you'll find that those parts you mentioned have no bend at all to the side inlet. So that means you can't use the side inlet for a drain connection.
Got it. How about a 2" 1/4 bend into the top of one of these?
 

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wwhitney

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I'm 99% sure that is OK. If the lower fitting were a 3x2x3 san-tee, it would definitely be fine. And I believe the low heel inlet quarter bend can be used as a 3x2x3 san-tee (and only used as one, i.e. the 2" has to be up), it's just that they don't make a 3x2x3 san-tee and make the low heel inlet quarter bend instead.

You could obviously use a 3" san-tee with a 3x2 bushing in the top, not sure if that makes any difference vs the low heel inlet quarter bend. And of course if you are height challenged, use a street 2" 1/4 bend on top.

Cheers, Wayne
 

Mikha'el

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Underground is in - of course we changed the guest bath layout in mid rough-in, deleted shower, moved WC... oh well, it works.

Back to that funky upper floor shower tie-in, a couple of options mocked-up - please comment on which is "more" correct:

Option A: vent up through interior wall, wye in after master bath group (not enough headroom to drop it in vertically):
shower drain A.jpg


Option B: vent up in exterior wall (trap arm will be longer) - drop into vertical wye in stack:
shower drain B.JPG


Thanks again for all the help,
Michael
 
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wwhitney

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Both are fine, assuming I understand correctly that we are just looking at how the shower trap on the left is being vented, and the other 4 openings are all drains already vented (or in the case of the rightmost opening, a WC that is being wet vented).

Note that in A, space permitting, you can potentially remove the 45 after the san-tee (or replace it by a 22.5) by rolling the 3x3x2 combo up. (But maybe that takes up more height, not sure, and you are height limited).

And in B, space permitting, you can potentially eliminate the last 90 in the shower fixture drain, by having a longer section that's at 45 from vertical. (But maybe there's an obstruction there you are jogging around.)

One more option for you, which is weird but I think OK: at the top of the 3" stack put in a 3x3x3x2 sanitary tee with right hand sanitary side inlet (make sure it's not a straight inlet), and then just plug the top entry.

Cheers, Wayne
 

Mikha'el

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Both are fine, assuming I understand correctly that we are just looking at how the shower trap on the left is being vented, and the other 4 openings are all drains already vented (or in the case of the rightmost opening, a WC that is being wet vented).
Yes - everything else is wet-vented via the lavs.

Note that in A, space permitting, you can potentially remove the 45 after the san-tee (or replace it by a 22.5) by rolling the 3x3x2 combo up. (But maybe that takes up more height, not sure, and you are height limited).
Tried that, not enough headroom.

And in B, space permitting, you can potentially eliminate the last 90 in the shower fixture drain, by having a longer section that's at 45 from vertical. (But maybe there's an obstruction there you are jogging around.)
Possible - it's just a big furr-out.

One more option for you, which is weird but I think OK: at the top of the 3" stack put in a 3x3x3x2 sanitary tee with right hand sanitary side inlet (make sure it's not a straight inlet), and then just plug the top entry.
Hmmm... supplyhouse might have one of those.


OPTION A v2.0:
After staring at these for awhile I did some re-measuring - might be able to stretch the shower trap arm to wye-in upstream of the master bath WC and omit the vent... looks like it could be less than 60". ;)

shower drain A v2.0.jpg
 
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Mikha'el

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More thinking...

1. The shower has to wye-in horizontally if it's on a wet vent, correct?
Is it a problem if the trap is above the level of the vent?
I was going to drop the trap arm into a vertical sweep and into a flat wye.
Except - oops - I think this creates a sort of S-trap?
Not sure if this example applies:
Seattle - wet vent example 4.jpg


2018 NSPC 12.8.1 has an exception if the vertical section of the drain pipe is one size larger than the trap inlet.
Can't find a similar exception in 2018 UPC 1002.4: Vent pipe opening shall not be below the trap weir...

Assuming Item 1 can be resolved without a separate shower vent:

2. With a double lav (2 dfu), bathtub (2 dfu), shower (2 dfu) I'm into a 3" wet vent per 2018 UPC - can it be 2" up until the shower is picked up?
2018 UPC - 908.2.2.jpg


I've seen "no reduction in wet vent" references, but they might be quoting IPC or ??
Also looking at the master bath in the sketch below - the floor drain confuses things a bit, but it appears to show 2" until the load exceeds 4 dfu, 3" beyond.
upc_wet_venting_bathrooms.jpg

Thanks again!
Michael
 
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wwhitney

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1) The trap weir rule controls. You need to comply with UPC 1002.4, and that almost always means that the fixture drain has to tie in horizontally with the wet vent. The NSPC exception is unusual and I recommend sticking with the UPC.

2) Yes, the size of any section of drain, which is also a wet vent, is based on the DFUs draining through that section. If it's 5 of more, it needs to be 3"; otherwise it's 2". I assume this is in reference to the upper bathroom in the drawing in post 20. For that branch you need a 3" line starting at the shower combo (3x2x2 combo).

Cheers, Wayne
 

Mikha'el

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1) The trap weir rule controls. You need to comply with UPC 1002.4, and that almost always means that the fixture drain has to tie in horizontally with the wet vent. The NSPC exception is unusual and I recommend sticking with the UPC.

2) Yes, the size of any section of drain, which is also a wet vent, is based on the DFUs draining through that section. If it's 5 of more, it needs to be 3"; otherwise it's 2". I assume this is in reference to the upper bathroom in the drawing in post 20. For that branch you need a 3" line starting at the shower combo (3x2x2 combo).

Cheers, Wayne
Thank you Wayne for confirming. I'll run the individual vent for the shower, no way to bring it in level with the wet vent.
 

wwhitney

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no way to bring it in level with the wet vent.
Just to be 100% clear, it doesn't have to come in "level" (rather, at minimum slope), it just has to meet the trap weir rule. UPC limits a 2" trap arm to 60", which at minimum slope of 1/4" per foot is 1-1/8" drop. So if you use minimum slope, you've got 7/8" to spare at the end. You could connect to the wet vent via a wye plus 45 rotated up by at most 7/8".

Cheers, Wayne
 

Mikha'el

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Just to be 100% clear, it doesn't have to come in "level" (rather, at minimum slope), it just has to meet the trap weir rule. UPC limits a 2" trap arm to 60", which at minimum slope of 1/4" per foot is 1-1/8" drop. So if you use minimum slope, you've got 7/8" to spare at the end. You could connect to the wet vent via a wye plus 45 rotated up by at most 7/8".

Cheers, Wayne
Right - except the wye for the master bath WC is in the way, downstream of this connection. :(
 

wwhitney

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This is the lower bathroom in the diagram in post 20, right? [BTW, good catch on the wet vent size error on the upper bathroom, I drew the shower-WC section as 2" but as we discussed it has to be 3".] If you're following the UPC, that limits the wet vent to a single bathroom group, you'd need to combine it with the WC/lav in the lower bathroom (since the other wet vent already has a shower on it).

So depending on framing, you do have the option to bring the lav drain down "below" (on the page) the WC drain, so that the shower can hit the lav drain wet vent before the WC. Or you have the option to decide to plumb that bathroom to the IPC or the Washington state amended UPC, both of which would allow the shower to join the wet vent downstream of the WC. [And the IPC would allow a 96" long 2" trap arm.]

Cheers, Wayne
 

Mikha'el

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This is the lower bathroom in the diagram in post 20, right?
Yes, the shower in the lower bathroom, but trying to wet vent it with the master bath.
I've been basing my layout on your sketch in post 18 - was assuming a "bathroom group" under UPC doesn't necessarily mean all the fixtures have to be in the same physical room - as long as it's no more than double lav/tub/shower/WC.

Heck, I'm from Washington, could just make it easy on myself since I'm in no-man's-land for inspection. ;)
 

wwhitney

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Yes, the shower in the lower bathroom, but trying to wet vent it with the master bath.
But as you say, a bathroom group has at most one shower, so under the UPC, you can't wet vent the lower shower with the master bath, since that branch already has a wet vented shower. You'd need to wet vent it with the lower bathroom group.

In post 18, the lower shower drain is individually vented, so it's fine for it to come in after the master bath wet vent ends at the WC.

Cheers, Wayne
 

Mikha'el

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But as you say, a bathroom group has at most one shower, so under the UPC, you can't wet vent the lower shower with the master bath, since that branch already has a wet vented shower.
Yes, but I was thinking it could be a mix/match of fixtures between the two groups (for clarity I'll say the lower/main bath is #1, master bath #2):

first group = double lav #1/shower #2/WC #1
second group = double lav #2/bathtub #2/WC #2 - and I was trying to wet vent shower #1 into this group

Working on an alternate layout based on UPC w/ Home State amendments...
 

wwhitney

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BTW, if you move the master bath 3" drain to between the wall and the WC, then the main shower could join that line from the left, and downstream of that the WC could join the line from the right.

Cheers, Wayne
 

Mikha'el

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BTW, if you move the master bath 3" drain to between the wall and the WC, then the main shower could join that line from the left, and downstream of that the WC could join the line from the right.
That joist bay is tighter, but good call - I'll take a look.
Would have to re-think how the two groups join ahead of the stack.
 
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