Trying to add a sink. Is it okay to tap into an existing drain line from up stairs, if I add a mechanical plumbing air vent at new sink to avoid p-trap
Old plumber shows how to install a Y fitting in a sewer line (drain line) using ferncos. - YouTube
Denver Tap Repair | Denver Sewer Repair
Sewer Line Repair Replacement | Underground Services *FIRST*
Flexible Tap Saddle Wye, for Pipe Size 4" - Pipe Fittings - Amazon.com