Adding a utility sink to garage

[tcampbell44]

Hello. I would like to add a utility sink in my garage but am not sure how to properly connect the drain so it will drain correctly and meet code. The sink will be installed against a wall that is adjacent to the basement where the drain stack is located. Please see image to see my current setup (sorry the water softener is in the way). There is a 3" main drain line that runs horizontally against the wall and then there is a 2" vent line that is attached to it vertically. This vent pipe I think is technically a wet vent because the kitchen sink and dishwasher above it drain through that line. The 2" washing machine standpipe is also connected into this 2" vertical line. Not sure if I am allowed to just connect the new sink into the vertical line similar to the way the washer standpipe is connected. I made some diagrams of possible options I think might work to connect the sink. I would appreciate if someone could please let me know if any of these would work and be code compliant in NJ. Thank you in advance!

 

[MicEd69]

I'm not familiar with the New Jersey NSPC but sketch 1 should be fine provided the length of the horizontal line from the P-trap weir to the vertical drain line isn't longer than that code allows. Using a 2" drain from the sink will increase that distance as it is dependent on the drainpipe size. Sketch 2 is a BIG no. Flow from the washing machine will back up into the sink drain line. Sketches 3 and 4 have an issue with the dry vent connecting to a wet vent.

If AAVs are allowed, you could use that as the sink P-trap vent if the distance to the vertical drain line is too far. Also, I assume your garage is heated as I think New Jersey does have freezing weather.

 

[tcampbell44]

Thank you for your reply. I checked the code and it looks like the max length of trap arms is 5' for 1.5 inch pipe and it is only about 2' from the wall to the vertical drain pipe, so that is not an issue. My garage is not heated but it is attached, so the temperature does not get below 45-50 degrees in the winter. Last night it was 18 degrees outside but it was still 50 in my garage. The basement is heated so I think I can set it up so the P trap is on the basement side of the wall so I would not need to worry about the water in the trap freezing. Not sure if that is really necessary though.