Install an Air Admittance Valve on drain lines? Home › Forums › Public Forums › Drainage & Sewerage › Install an Air Admittance Valve on drain lines? This topic contains 0 replies, has 1 voice, and was last updated by Jenny Clift 6 years, 5 months ago. Author Posts 9 Jun 2013 at 1:47 am #280136 Jenny Clift I am attaching a crude drawing. I have a first floor laundry room area with toilet, shower that was an addition to the house (before I moved in). When we flush the toilet, we sometimes get a gurgle in the washer drain. Also when the washer drains we sometimes get odors. I think itâ€™s a ventilation problem. The original main line (going to kitchen and upstairs bathroom) has a main vent stack on the roof. I am wondering if I could put an Air Admittance Valve on the Laundry room drain lines (http://www.oatey.com/products/air-admittance-valves/aavs/sure-vent-air-admittance-valve-20-dfu-capacity), if so then what size and where is the best place? I can get under the floor and access most of the pipes. I can get to the toilet drain and to the drain line connecting the sink and washer.The toilet drain is 3â€, and the washer, sink, shower is 1/12â€. Thank you-C Crude Drawing Author Posts You must be logged in to reply to this topic.