Plumbing Questions & Answers

Question:

If I’m hooking up a floor sink and tying into a 4″ pipe with a lateral less
than 2 ft., the 4″ is down 2 ft. from the water closet, which I have the
4″ main vent between, on it’s back, would I have to vent that 2″ floor
sink?

Answer:

As long as you are within 5 feet of the 4″ vent you would not need additional venting.