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Install an Air Admittance Valve on drain lines?

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Jun 08, 2013, 12:10 PM
Install an Air Admittance Valve on drain lines?
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 (, 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

Jun 08, 2013, 07:03 PM
..gurgleing drains are a vent issue. its due to:
a pluged vent
a semi stopped up drain
both the above
as per your post, you say the washer and shower drains are 1 1/2" drain lines? bingo !!!!
a drain works like a straw full of coke,
put your straw in a glass of liquid. put your finger over the end of straw. lift up the straw. liquid stays in straw. no vent..take your finger off..vent
a 1 1/2 drain line is to small to be used as a drain the inside of the pipe gets a small amount of gunk stuck to its sides and it cuts off the free flow of air. plugged vent
a drain must have a cross sectional area big enough for liquid and air to occupy the space at the same time. "finger off the straw"
a 1 1/2 line WILL work when first installed. because its new, the sides of pipe are clean. after time soap scum builds up on the sides due to lack of scouring and the more it builds up the less it vents. then the pipe glugs or gulps to get air
rod your drains out, if it persists replace piping up to code standards or learn to like it*****?v=vn7bkncf1_E