The main vent stack for the house is in the southwest corner by the first floor bath. The kitchen is about 18′ away and, I’m guessing, hasn’t been properly upgraded in 40 years. The newly remodeled bath on the second floor is about 20′ north of the main vent. Some idiot used a compression under-sink style P trap for the tub. Thus the leak on the living room ceiling.
So, on to the questions. The kitchen sink is under the window on the east wall. I have 8″ from counter top to lower window sill. The dishwasher I will need to put on the north wall about 7-8 lineal feet from the sink due to space restrictions. I’m willing to bet that there is no venting. Can I run a 2″ vent under the window above sink height, up the wall, around the corner, and pick up the vent from the dishwasher drain? I then plan to carry the 2″ vent up through the wall to the attic and pick up the new 3″ vent for the upstairs bathroom there. Yeah, I’m tearing out 8′ of wall in one bedroom to do the plumbing properly. No choice in the matter since obviously the remodel was never done properly and most certainly without permits or inspections.
I’m not a plumber but I’d like to know if I’m all wet from the start. I hate having inspectors laughing at me! I know local codes may vary, but UPC should cover me, I hope. Is the plan sound or do I need to up the kitchen vent line to 2 1/2″ due to the length of the run?