Question about Washing Machine Vent on Same Drain as Laundry Sink

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MudddyJeep810

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First off, I am not a professional plumber but I have done quite a bit of minor plumbing, relocating vanity drains, relocating shower drains, etc. For this one I have more than one fixture draining into the same pipe and I am unsure of the codes regarding this.

In my laundry room we had a washing machine that was previously draining into a laundry sink and we are remodeling the room to add some cabinetry in the location of the laundry sink. We are eliminating the basin style free-standing laundry sink, and doing a drop in that will be centered in a sink base cabinet with other cabinets on either side of it. This means I can no longer drain my washing machine into the launddry sink and I need to plumb a new laundry drain.

The way it was before, the old laundry sink just had a P trap and then ran through the studs to the corner of the room, approximately 5 feet away. In this corner, the drain went down under the cement slab and tied into the main. Where the drain went down, there is also a vent that goes up through the roof.

What I want to do is move the laundry sink a few feet closer to the corner, and then where the washing machine will be I want to plumb a washing machine drain/supply box. With how the plumbing is ran where the drain ties into the vent and goes into/under the cement slab there are quite a few fittings, so it's really only possible to have the single horizontal drain pipe (with pitch) that connects to both the new laundry sink, and the washing machine drain.

So now to my questions. What is the max distance from the laundry drain P trap that the vent can be? Ours will be roughly 8 feet away. Is this ok? Second, will I need to add an additional vent on the washing machine side so as to not pull water from the sink P trap when the washing machine is draining? I was thinking I could add an air admittance valve in the upper section of the wall if necessary. It isn't really as feasible to add a vent out the roof at this end.

I included the design of the new laundry/ bathroom. Thanks in advance for your responses.
 

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WorthFlorida

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This what you want to achieve. This vents both traps. 8' is the max distance to the vent with 2" pipe.


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Reach4

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So now to my questions. What is the max distance from the laundry drain P trap that the vent can be? Ours will be roughly 8 feet away. Is this ok? Second, will I need to add an additional vent on the washing machine side so as to not pull water from the sink P trap when the washing machine is draining? I was thinking I could add an air admittance valve in the upper section of the wall if necessary. It isn't really as feasible to add a vent out the roof at this end.
Under IPC, with a 2 inch trap arm, the max distance from the output of the U of the trap to the sanitary tee is 8 ft.

This will probably not work for you, but you did not label where the standpipe will be.
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Jeff H Young

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My guess its not a 2 inch line but if it is you can be 8 ft also with aav you might make it legal with 2 inch . If you only have 1 1/2 Personally I wouldnt plumb it in 1 1/2 for a customer but If you only have 1 1/2 and its in good shape fingers crossed you might have saisfactory results I just cant advize confidently
 
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