Add washer standpipe and vent to existing drains

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Boilermaker

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20220209_201200.jpg

I'd like to install a washer standpipe in this laundry reno, instead of just draining through sink on left. I've drawn one proposal for the standpipe to p-trap, tying into drain under the existing sink drain, with vent tying into the horizontal vent run above. Is this an acceptable setup? Any better ideas?

I appreciate any ideas you may have.
Thanks.

Additional details:
- opposite side is a bathroom with sink drain coming into the image from the right and tub drain in lower left.
- the main stack from upstairs bathroom is also on the left
- there is also some space further to the right if it makes more sense to drain into the 4" down there, but space is at a premium everywhere
 

Reach4

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In IPC, a standpipe plus anything else should go into a 3 inch pipe. Maybe you could use the 3 inch pipe with a double 2-inch santee and a common vent? Or have the standpipe go to a lower santee if there is room? Like the standpipe you drew but flipped left-right.

Also, the vent horizontals are supposed to be 6 inches above the top of the standpipe.
 

Jeff H Young

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cant share a wash macine and other fixture on less that 3 inch Soooo. Id cut into the upstairs stack with a 3x3x2 santee for wash machine and revent into the other vents. the other 3 inch that is there I think wet vents a w/c and likely not allowed in your code but im not certain they both look equally easy though So Id prefer using the second floor stack
 

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Ok, so if I'm understanding correctly this would be fine as shown under UPC (assuming vents are 6" above flood for all). Call that option 1. But under IPC, the problem under option 1 is capacity, the lav + standpipe would need 3". If I flip it to the 3" on the right, still venting to the horizontal vent above, I would have the capacity I need, but would now be wet venting a toilet with a standpipe, which is also a problem under IPC. Call that option 2. So then option 3 would be to drain to the stack on the far left, with venting plan still the same.

Sound right?

So option 3 would be the only IPC approved choice. Among options 1 and 2, which would be the lesser evil from a practical performance standpoint, if they are both UPC approved?

Thanks for all the responses, very helpful.
 

Reach4

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Oh, that is a toilet under the 3 inch being wet vented. Adding the standpipe to that 3 inch would not be allowed.

Standpipe combined with something else in 2 inch used to be allowed under IPC and is still allowed for much of the country. I was kinda wondering why there was a handy 3 inch there. I should have thought of that wet venting a toilet. For rework the inspector might be OK with your original plan, because the 3 inch option violates the wet venting for the toilet and would be the greater sin. Maybe the inspector would be OK with the original plan.
 

wwhitney

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What's underneath? How about putting the standpipe on the right, and taking the drain down below to tie into the 3" branch serving the bathroom group, after all the fixtures?

Cheers, Wayne
 

Boilermaker

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What's underneath? How about putting the standpipe on the right, and taking the drain down below to tie into the 3" branch serving the bathroom group, after all the fixtures?

Cheers, Wayne
I like the idea. Will consider, but thinking that concrete work might not be worth the standpipe vs just sticking with the drainhose to sink as it was before. Definitely worth considering though.
 

wwhitney

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concrete work
Ah, it's on a slab, that does favor an above floor solution.

The current laundry sink, is the drain through the slab 2"? If so, you could use that for the laundry standpipe (replace the current san-tee with one pointing towards your standpipe.) And then cut a new san-tee or combo into the 3" stack on the left, for the laundry sink. The laundry sink would need a vent-takeoff before the left hand 3" stack, and the vent can rise up to join the existing vent header.

This presumes that the 2" drain through the slab hits a 3" line under the slab, which seems very likely.

Cheers, Wayne
 
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Jeff H Young

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It seems easy enough to meet code connecting to 3 inch stack at far left. I've seen homes from the 40s or 50s with laundry going to a sink but nothing built in last 50 years unless its a low budget remodel or rental. But its a workable and legal option not a thing wrong with it. just very uncommon to see work done that way in a modern home . I've never seen a new home like that
 

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So, I've decided to go with majority opinion here. Laundry sink tied into the 3" drain on the left with a vent takeoff from the trap arm. One question as I'm in process :) how do I slip the 3x3x1.5" santee into that existing 3"?? I see that the 3" has 1.5" of gluing surface as opposed to 3/4" on the smaller pipe. Do I need to use all 1.5" or do I try to use that extra 3/4 as slop to fit it in like a slip coupling? And that's assuming I can even bend the 3" pipe to slide this thing on from below. Or should I be using some appropriately spec'd rubber couplings? Apologies if this is a basic question.
 

wwhitney

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Briefly, you use two shielded rubber couplings. You put pipe stubs into your santee top and bottom, with at least 1" of clean pipe at each end for the rubber couplings. You arrange that the cut in the stack is 3/8" longer than the the insert assembly: 1/8" for each coupling stop, and 1/8" for play. The rubber couplings get installed one side of each, and then folded back over themselves for installation.

Cheers.
 

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Thank you. I assume this would be a superior solution to trying to insert a slip fitting substantially further up the pipe so that I might be have enough play to get the Santee in without rubber?
 

wwhitney

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Thank you. I assume this would be a superior solution to trying to insert a slip fitting substantially further up the pipe so that I might be have enough play to get the Santee in without rubber?
You'd need two slip couplings. They are harder to use than shielded rubber couplings. Wayne
 
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