New Laundry Drain - Vent Question
I am installing a washer/dryer in a bathroom closet in a 5 floor condo. I'm on the 1st floor and can access my plumbing through a crawlspace. I have my toilet, bathroom sink, tub, and kitchen sink drains each separately tie into a horizontal pipe that ties in a vertical sewage stack. I don't have a vent pipe anywhere. The washer standpipe (with p trap in-wall) would be attached to the horizontal pipe, and be the closest drain to the sewage stack (2ft away). My question is, how do I vent this?