I recently purchased this house and decided to remodel the laundry room. After looking at the plumbing I noticed that there were no vents for the Laundry or the Kitchen sink. My question is can I tie in one vent for both rooms? The washer box is new and I have run 2" PVC down to a trap under the floor. I plan to leave the trap and run towards the kitchen sink (about six feet) and tie into 2" sink drain which runs down into 2" cast and ties into main line leaving the house. The Kitchen sink is trapped above the floor in the cabinet. Can I install a vent between the washer trap and the tie in under the Kitchen sink and vent both rooms? The only other vent is in the main cast line just after the toilet. It's a 3" cast pipe.

Can I install a vent between the washer trap and the tie in under the Kitchen sink and vent both rooms?
No! Every fixture that has a trap must be vented. You may vent the washer and the kitchen sink separately and tie them together to go out the ro0of or revent back into the main vent. Your way wold leave the kitchen sink with a illegal "S" trap and a problem for the washer if the run from the washer trap to the vent takeoff exceeded 5 feet. If local codes permit consider installing a AAV,(Air Admittance Valve) downstream from each trap. Good luck, Tom Regards, Tom