Drain Layout Approval - Full Bathroom + Bar Sink

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Mr.T

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On to the next bathroom that needs to be completed. This should be pretty straightforward. Is this layout acceptable (see attached pic)? A few questions:

1) Is the single 2" vertical stack vent appropriate for the water closet and the shower?
2) Is the best choice a 3" double wye (with reducer for the 2 "shower trap arm of course) for the water closet and shower and then a 2" santee above that for the lav drain?
3) I assume that since the double lav is over 8' away from the stack, I will need to re-vent those, correct?

Note, I intend to vent the bar sink that is on the first story up to the vent. As always I really appreciate the help on this forum!
 

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wwhitney

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1) Sure.

2) Definitely not. The vent connection for the shower needs to be at an elevation no more than one pipe diameter below the trap outlet. So if the stack is to vent the shower, you can't use a wye to connect the shower trap arm, you must use a san-tee. This doesn't apply to a WC, it could connect with a wye and still be vented via the stack.

So you could stack the following fittings (from bottom up): 3" wye or san-tee for the WC, 2" san-tee for the shower, 2" or 1-1/2" wye or san-tee for the lavs. Of course you're not likely to have enough height for all that. You could use a san-tee with sanitary side inlet to bring the lavs and shower in at the same elevation. Or you could connect the lavs drain to the WC fixture drain before the stack, which would cause the WC to be wet vented via the lav.

3) You show the drain for the lavs turning down from the trap arm elevation before it goes horizontal, and you must provide a vent at the trap arm elevation, as per the rule mentioned for the shower. So with the geometry shown, the horizontal distance between the lavs and the stack doesn't matter.

Cheers, Wayne
 

Mr.T

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Wayne,
As always you are supremely helpful. I don't know what I was thinking about wye for the shower. I was being dumb there.

As it turns out, I have a decent amount of flexibility with this layout. This is all coming down from the second story, the stack will be behind a wall and the W/C and the shower lines will be in a small soffit and could drop below the joists. The lavs will have to go through the joists and frankly, it would be easier to run 1-1/2" vs 2" for clearance to a heat duct and also to minimize the hole size through the joists. Although I have a 2" double fixture fitting I was going to use for the lavs so I don't think I can reduce from 2" to 1-1/2" can I?

So, I think my optimal layout will be basically as you suggested:
- 3" wye for the water closet (Any preference from the pros on a wye vs a san-tee here?)
- 3" san-tee with 1.5" side inlet (One of these fittings, right?)
* https://www.supplyhouse.com/Spears-P416-337-3-PVC-DWV-Sanitary-Tee-w-1-1-2-Left-Side-Inlet
* https://www.supplyhouse.com/Spears-P416-338-3-PVC-DWV-Sanitary-Tee-w-2-Left-Side-Inlet
* I would obviously use the 3" with a reducer for the shower side)
- 2" san-tee upside down to feed the bar sink vent
- 2" PVC up to the attic from there for the vent

Look good?
 

wwhitney

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Yes, to my knowledge double fixture fittings don't come with a 1-1/2" outlet. And if the double lav is going to be wet venting anything, you'd need a 2" wet vent anyway.

If you are using the stack to vent the shower, then the WC connection needs to be below the shower connection, as I understand you intend. So ignoring the lav for the moment, 3" wye or san-tee for the WC, with a 3x2 bushing in the top entry, and a 2" san-tee for the shower, that would be your minimum sizing.

Then you can bring the vented lavs drain in anywhere you want. Into the WC line to wet vent it. Into the shower drain to wet vent it (in which case the vent stack above would not be required, as that would also wet vent the WC). Into the stack at any elevation. A san-tee with side inlet would be fine to bring it in at the elevation of the WC or shower.

If you want to use a 1-1/2" drain for the double lavs, then that drain would need to connect to the stack. Since there are no double fixture fittings, you could split your lav stack to use two san-tees for the two lavs, with a wye above and below to rejoin the drains/vents.

Cheers, Wayne
 

Mr.T

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Had to go out of state for a month for some family stuff. Finally back to working on the house. Decided on a possible change to the layout. The following pic has two alternatives and is a plan view of the layouts. I think both would work to wet vent the entire bathroom group. (Note that there would be no vertical vent off the top of the stack).

Alternative one is a bit easier to route in the space I have available. Will both work though and is one preferred functionally? Thanks!
 

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wwhitney

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I assume the WC drain is 3" and the other drains are 2".

Alt 2 works fine as long as the shower trap arm, from trap-outlet to the wye or combo where it joins the lav drain, falls less than one pipe diameter (2"). It needs to fall at 1/4" per foot, but looks like it would only be 4' long (if to scale), so that shouldn't be a problem.

Alt 1 works with one qualification. If I understand correctly, you are using a 3x3x3x2 san-tee with right side 2" inlet, capping the top entry, and use the 2" shower/lav drain coming in to wet vent the 3" WC also coming in. Fine in my book but sufficiently unusual some might disagree.

Alt 1B would definitely work, which is like Alt 1 but the 5' section running up and down the page is, say, 1' to the left, so it can join the WC drain with a horizontal combo. Then the 3" branch drain just turns down into the stack with a 3" quarter bend (which is what I assume Alt 2 is doing).

Cheers, Wayne
 

Mr.T

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Wayne,
Once again (for probably the 15th time over the last year plus), thank you. You are correct in all of your assumptions. Actually, your idea of Alt 1B may be the best bet simply because I have all the fittings necessary to do that vs. having to order the 3x3x3x2 San-Tee with Right Side inlet and also a cap. Really 1 or 1B will be dictated by overall room and ease of clearance to any other obstructions (wiring, HVAC). I'll add a pic once I get it dry fit or just finished. Thanks again!
 
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