Install an Air Admittance Valve on drain lines?

[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 it’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 3”, and the washer, sink, shower is 1/12”.
Thank you
-C

Crude Drawing

[Author]

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