I know this topic has been covered extensively, not only here but all over the web. The problem is that there is so much conflicting information out there. I have gathered the following from what I have read here. 1) It seems that if I want to do this by code, I can not just tap into the washer stand pipe, even though it has a trap and a vent, I would need to create a separate drain line and tap into the vent stack. Also I have read that I may be able to meet code tapping into the washer standpipe as long as I don't put a trap on the sink since this would create a double trap situation. The risk with this would be water backing into the sink basin during wash cycles. Correct me if I'm wrong with these assumptions. I have enclosed 3 pics of my situation. It is a 5 year-old house and the laundry area is in the basement as seen in the photos. The first pic shows the drain stack (vertical 5") on the left, the vent stack (Vertical 2")in the center and the washer stand pipe to the right. The second pic shows the sink where it will sit and the third pic shows the view from the sink drain point toward where it would need to connect. I am a very capable diy'er but plumbing is certainly not my strongest suit. I want to meet codes with this install and also I am not thrilled about water backing up into the sink basin during the wash cycle. So my question is; Looking at my pics, what is the best way to add a drain for my utility sink?

Hi Cuseguy...

OK... as in first picture, I would have you cut the 1.5" pipe as indicated and then repipe all so that the 1.5" pipe picks up the utility sink... should just need some primer/cement, pipe, couplings, a new ptrap, a couple 45s, a street 45 and a female adapter and teflon tape OR an 1.5"x6" flanged tailpiece, an 1.5" pvc desanco fitting, and an 1.5" nut.

Then I would have you cut a 3"x2" wye into the 3" stack as shown below in 2nd picture... run this as drawn or as needed, but be sure to add the vent (connecting it at about 48" off the floor into the 1.5" vent for sink), the cleanout and a 2" ptrap with standpipe a minimum of 30"-36" tall.

Be carefull to support the stack properly as you cut/work with it. If stack/pipe will not rise enough to slip the fitting into stack you may need to purchase a SHIELDED CLAMP to make this work.

That is my thoughts on this... let me know if you have any questions...

MARK

Thank you so much Mark, I really appreciate your help!

I think I've got it. I was on the right track with the additional 3x2 wye, but I wasn't confident enough to just do it without asking a professional. Very good diagrams... thanks again. Off to HD I go!