Hi,

I would like to add a utility sink to an unfinished basement section. The proposed site is on the opposite side of the wall from an existing guest bath. I would like to tie into a vented waste drain for the bathroom sink. The vertical vent is 2". The sink drains through standard pvc at the required 1/4"/lf slope. I am unsure where to actually tap in to keep the vent operating properly for the existing sink? To avoid problems should I make a re-vent and tie into the vent well above the connection or is it OK to change out the waste tee for a waste cross and have everything still vent properly? Is there another option that I haven't considered? Picture attached for clarity.

It looks like you are familiar with wet venting since that appears to be what you currently have. Is the existing sink 1 1/2"? Using a cross is fairly common in back to back bathrooms and since the vent is already in place, it should work. I have a similar connection in my basement, cross is fed from a vanity on 1 side, a utility sink on the other and an AAV on the top.

Yep, 1 1/2. Thanks for the confirmation. My hesitation comes from reading recently that you shouldn't have 2 P traps on the same wet vent "with a few exceptions", but the article didn't go on to list the exceptions! Was hoping this is one. :)

I think that refers to 2 P traps connected on a single line like under a double bowl kitchen sink. Not uncommon to find one wet vent draining an upstairs and downstairs vanity if your local code allows, Some double vanities will have 2 P traps.

Hey Ma0641...

What does this mean, "Not uncommon to find one wet vent draining an upstairs and downstairs vanity if your local code allows"..

No codes anywhere that I know of allow you to have a sink on one floor and install another sink on a floor above or a floor below the first sink using the same vent... would siphon the sink trap, for sure! However, reventing the sink back above the original sink would work, but that's not wet venting, it's individual venting. Wet venting is strictly limited to single floor use!


Melissa, how far is this utility sink going to be from the sink drain you want to connect into? Also, will you be draining a washing machine into the sink? Let me know...

Mark