Best way to wet vent a washing maching and utility sink?

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K-Man

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I inherited a small mess that I am cleaning up. The basement washing machine and utility sink wet vent into a 1-1/2" riser that goes thru the concrete slab, w/ an AAV -- I am stuck with that situation (these were installed by a plumber for the previous owner.) I don't know the DFU but if not large enough I'll change the AAV (or add a second.)

The W/M trap was cracked -- see pix -- (and the drain for the U/S is horrendously stupid - notice the copper to galvanized to pex -- I am starting anew with all that.) I may finish that room at some point, so might install a W/M supply/drain box - not sure.

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Q1: The wye for the U/S drain - isn't that a No-No -- should have been a San Tee??

Q2: I'll locate the W/M riser/trap 12" above the slab - should I use 2" (and also there to the slab) even though the thru-slab is 1-1/2?

Q3: I plan to use an S-Tee for the W/M drain. OK?

Q4: Any reason to lower the U/S drain and stack the S-Tee onto the W/M S-Tee (I'd think it's best to keep as much separation as I can)?

Q5: Concerned w/ the high W/M flow/pumping - do I need to back vent the W/M drain (or I could add a second riser/AAV??)

Q6: (just curious)What's the reasoning for the W/M trap 12"-18" and a max 30" riser?

Q7: This pic floats around - isn't the wye for the W/M a No-No? (or is that only when a wye is on the trap arm itself?)
And the sink drain looks too steep - the vent inlet looks to be below the trap weir level?


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Thanks for looking at this!
 

Reach4

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Q1: yes.

Q6: The reason cited for the UPC is to prevent there from being enough head to encourage siphoning of the trap. Since WMs typically end up with low flow, I suspect the trap would get refilled, even if it did siphon. However NC does not use UPC, but rather IPC. IPC is more tolerant than UPC, and allows a much taller standpipe. https://up.codes/viewer/north_carolina/ipc-2015

The totally code-compliant thing to do with your 1.5 inch drain pipe is to only connect the laundry sink, and discharge the WM into the sink. However I know that in practice allowances are often made for existing hard-to-change things, maybe a standpipe in addition to the sink would be permitted. I expect that is a local decision. I am not a plumber.
 

Terry

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The laundry tray can't be wet vented over the washer. They need separate vents, which can combine above 42" and go to a single vent.
The vertical for the trap arms will come off of a santee fitting, not a combo or wye.

The washer gets a 2" trap and standpipe. It can have a 1.5" vent.
The laundry tray is 2" except for a 1.5" trap, trap arm and vent.

Santees on the vertical for the trap arms.
The combo on it's back for the vent is what inspectors like. Vertical to horizontal, a wye or combo.
Horizontal to vertical on the trap arms, a santee.
 
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K-Man

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Terry -

THANK YOU (for your guidance/pix and making such a wonderful resource available.)
The AAV looks like it may be non-compliant, or at least a Keeney (which I have heard leaks gas) so I will replace it (1-1/2 AAV Oatey is way higher than the 4 DFU that I need.)

Is it acceptable to use tees or santees on the vent, vs. the sweeps you show?

Are you concerned that the thru slab is 1-1/2" and will have the 2" washer and 1-1/2" tray to it? Would it be better to "choke off" with 1-1/2 above the floor? (I realize it isn't current code, but trying to make the best of a not so good situation.)
I really HATE to do it (because it isn't a "finished job") but if this were yours would you dump the washer into the tray and be done with it?

Odd that the Keeney prefab polypro washer standpipe/trap that Lowes carries is 1-1/2"???
 
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