Draining sink & washer to same standpipe?

[Jason W.]

All, thanks in advance for the help.

I’d like to add a utility sink near my washer. Currently there is one standpipe, shown in the picture and it does not vent through the roof, also no trap. Is it a big deal to drain both a sink and washer into the pipe?
I planned to expand left [pic] for the washer and add draining for the sink to the right. Rough sketch over actual pic attached.

any issues with this Approach, also should I add AAV to the top of the pipe since it doesn’t vent outside?

 

[Jeff Handy]

Is that standpipe plumbed into an old floor drain?

Or maybe a rough-in for a toilet?

If either of these are true, then there is probably a trap already under the floor.

You can verify a trap under the slab by shining a light down there, if you see standing water it has a trap.
Or the drain is clogged, haha.

Or poke a stick down, and if three or four inches of the end are wet, it has a trap.

 

[Jason W.]

Is that standpipe plumbed into an old floor drain?

Or maybe a rough-in for a toilet?

If either of these are true, then there is probably a trap already under the floor.

You can verify a trap under the slab by shining a light down there, if you see standing water it has a trap.
Or the drain is clogged, haha.

Or poke a stick down, and if three or four inches of the end are wet, it has a trap.

It is nearby/inline with a floor drain and the light showed some water, stick had a few inches wet, think you’re right. See any issues with me cutting in the T for the Sink drain?

 

[Jeff Handy]

The pros on here can advise, but I think you can run both down there.

Or plan B, just connect your new slop sink to the standpipe, cap the standpipe with an AAV, and run the washing machine drain over the side of the slop sink.
Capping the standpipe might help with odors.
Laundry has lots of fibers that will rot in the drain and create stink.

But I am not a pro, so wait for better advice as it trickles in!

 

[frodo]

just my thoughts
you say there is a floor drain inline with this pipe. that would lead me to believe that pipe is the vent for the floor drain

if you stacked the tees the way your drawing shows. i believe the washer would suck the laundry sink trap dry
but if you use a wye...like this

 

[Diehard]

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