Can a sink drain into a shower venting pipe?
I wanted a utility sink installed on the common wall of our garage and house. There was a vertical vent inside the wall near a bathroom and near the washer/dryer alcove. The plumber plumbed the drain into that vent saying that this was allowed by code if done in the right way. I didn't understand what would make it code compliant and would make it work properly, but he put it in and it has worked for 20 years.