Different question same bathroom...

I'm adding a washer hookup in a 2nd floor bathroom. Due to space and framing restrictions I'm not tying in to the stack on the second floor but have run 1 1/2 pvc drain down the outside wall to the basement, and joined the (vented) kitchen sink drain line about 3 feet before it joins the main 6? Inch waste line.

To vent the washing machine drain I've used an oatey inline vent.

1) is the difference between an in line vent and an AAV the spring? In other words the inline uses a spring to close and the AAV uses gravity to close?

Both of these are frowned upon by inspectors here but allowable by DIY with good reason (which I think I have)

2) should I spend the extra money and find a better AAV? The inline was all I saw at the local home depot/lowes.

Thanks again,

Steve

If you did not put at least a 2" line for the washing machine, expect slow drainage. The oatey, or studor vent is code compliant for housing, the cheaper black one is used on mobile homes. They are inspected by the DMV [dept of motor vehicles] the building codes are not enforced on mobile homes.

Thanks for the reply. I changed up to the Studor minivent, it just seemed like a better design than the cheap black one I had.

I originally wanted to run 2" drain but was having space problems making the turn down the wall and then turning under the floor over the foundation in the basement. The current drain is 1 1/2" and has never given us problems... Let's hope it stays that way...

You can thank Doug for this explanation. The inline vent is the cheap black plastic ones used in mobile homes. It is a simple spring check valve with a rubber disk. It costs about 5 bucks. The studor and oatey which costs about 25 bucks is kind of mechanical in that it has a little ball that blocks the port and is approved by the building code.
Thanks Doug, Tom

That 1.5" drain won't just be slow, it would likely over flow at the connection. The washer is going to pump a good volume with suds and 1.5 just can't handle it.

Well, That's not good news. I assumed that the 1 1/2 that is currently in use was working fine and I could use the same (the 2" hook up on the washer box did make me pause for a minute though).

After talking with the wife I find out that sometimes the washer backs up into the stationary tub next to it :( Guess I'm going to tear out some 1 1/2 and put in 2"

Can I step down to 1 1/2 just before the main in the basement?

If not, that means a new connection to the main, and a whole new problem,

Yep, the suds and the power pump of the washer are just too much for 1.5" pipe.