Adding basement utility sink

[clarinut]

I am looking at installing a basement utility sink next to a washer and dryer. The washer is currently draining into a standpipe with p-trap and pipe which leads to the right, directly into the main sewer drain stack. This stack is vented up through the house to the roof. The vent is 3" or 4" (not sure exactly). Every drain in the house is directly linked to this main drain/vent stack. This includes the washer, kitchen sink/dishwasher drain, upstairs bathroom sink, tub and toilet.

I would like to somehow connect the utility sink drain to either the washer standpipe or somehow into the drain pipe leading away from the standpipe or maybe directly into the main sewer drain. Any thoughts on this and why any of these ideas may not work? There are two pictures below of what I currently have set up.

The washer is on the left of the standpipe in the first picture. The horizontal pipe in the second picture is a continuation of the pipe at far right in the first picture. That pipe is leading directly into the sewer drain pipe.

The utility sink would be to the left of the washer because that is where the water supply is.
Thanks in advance for your help.

 

[Michael Young]

Remove everything all the way back to the rubber fernco. From the rubber fernco. Cut in a 3" WYE and turn the wye part of the fitting straight up. Install a TEE. On top of the tee (at least 6" higher than the flood level rim), you can install a studor vent. On the horizontal run, pull a 3" all the way over to catch the horizontal on your washer box.

 

[Sponsor]

 

[WorthFlorida]

What you have is a wet vent for the washer and it looks to be nearly 8' to the stack. Adding a sink further away you'll exceed the 8' horizontal limit for a 2" pipe before it must be vented. I'm not a plumber but I'm not sure what you have is proper venting. It's possible under the right conditions that the p trap for the washing machine can be siphon dry.

Adding an AAV after the washing machine drain p-trap at about the same level of the washing machine drain pipe may suffice the venting needs. Local codes may differ.

After the utility sink P-trap install an AAV above the flood level of the sink and run a 2" pipe and wye into the 2" drain pipe between the washing machine AAV and the waste stack. Maybe other will agree with this. I sent this before Michael Young responded.

 

[clarinut]

Thank you for the replies. Are you saying that what I currently have (something a reputable area plumber installed) may not be to code? What you are describing to remedy this and to add the sink and drain sounds a bit complex for me. I am kind of a visual learner. Is there anyway you could draw a simple layout for me? I would be most appreciative. Thank you.