We're renovating a kitchen and are moving the washer and dryer location (yes, it's in the kitchen space, no practical way around it). I'm using an AAV to vent. The walls the existing drainlines are 1 1/2". I know you're supposed to use 2", but I've stayed with 1 1/2" due to the thickness of my walls and the space I need for kitchen cabinets. I used an image I found on another thread there to model the installation. See the drawing below and here's the thread (https://www.askmehelpdesk.com/plumbing/do-vent-aav-valve-washer-drain-417618.html). However, when I tested it out by putting a garden hose in the line, it immediately overflowed. Then I realized I still had the plug in the AAV line, so I removed that (but did not install the AAV yet) and ran it again. Things aren't much improved. After a very short time the water will overflow and then takes it's sweet time draining. Is my problem with the AAV line? Do I need to run the vent back to the main vent? Is it the 1 1/2" line? I know there are tons of homes in our area with 1 1/2" drains, so it doesn't seem to explain it to me. I'm leaning towards the vent being the issue. There is also a pic below of my setup.

https://www.askmehelpdesk.com/attachment.php?attachmentid=48436&stc=1

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I should mention that pipe that goes up vertical out of the image goes just out of view to the AAV.

I see 2 X 90* short ells, vent ell? 90* long or 2 X 45 is needed horizontal to horizontal. How far to the main drain? How much slope? You can't bury the AAV in a wall, it must be accessible. If your design backs up with a garden hose, it sure will with a washer pump. Sure there is no blockage? If it takes a long time draining, you have a blockage or downstream vent issue.

"I see 2 X 90* short ells, vent ell? 90* long or 2 X 45 is needed horizontal to horizontal."Sorry, I'm not sure not sure what you're asking here.I'm adding a larger image to show the full installation. The drain connects to the old drain with the rubber union shown in the left corner. Then the main line is just out of the picture. So the full run is about 13 ft total. The new line is sloped 1/4" per ft. The AAV goes to an access panel, which you'll see more clearly at the top of the new pic. So it will be accessible. I did not test the line at it's original location, so it is possible it needs cleaned. However, when I tested the new installation, it seemed to me to overflow very quickly, which makes me lean towards a venting issue.Here's a stupid question, I did not have the actual AAV in place when I tested it. I just had the AAV line open thinking this would work just for the test. Would that have caused the line to drain so slowly?Thanks ma0641 for your help.

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An open vent will work better than one with an aav, especially the v200 shown in your diagram. V 200s are not reliable or approved; I prefer the Oatey or Studor brand of aav. Tubular traps ( and stand pipe ) are significantly smaller than 1.5" pvc pipe size traps, and, flow wise, more restrictive. You may be able to improve the situation by installing a full size trap, increase the stand pipe to 2" immediately above the trap, and make it 6" taller; I would also increase the size of the vent pipe to 2". A 2" stand pipe and vent riser will provide more capacity during the initial discharge flooding, and this will also help prevent suds overflow. l suggest connecting the washing machine and test all connections before closing the wall...

The problem is definitely at the galvanized drain pipe... probably choked down to almost nothing where it connects to the vertical pipe (especially if cast iron).

Use a flashlight to inspect inside the pipe. If clogged, you'll probably need a long screwdriver and a hammer to chip away at the solidified accumulation of sediment. If you can't clear the line at least 90%, cut out this section and replace with new pipe and fitting.

Good luck!

Oh, and like Mike said, get rid of that tubular ptrap and stand pipe... not only smaller diameter, but has nuts that will eventually loosen up and start to leak behind the wall. Install a Ptrap with no cleanout.

Stand pipe should be 30" tall - or taller - and 2" in diameter.

See if you can find better way installing that horizontal drain, before you cover up the walls, otherwise you will continue having problem with it.

Milo