Washing Machine P Trap

[Jim the dude]

Currently building a laundry room off of the kitchen. The floor will be the same level as the main floor of the house, which has a basement.
My question concerns the P-Trap for the washer. I assume an S-trap isn't allowed, so I am planning on using a P-Trap. Once the water drains into the trap, I need it to go down so I can use a 90 degree elbow to go through the rim joist of the house. Once the water goes through the P-trap, does the pipe have to travel a required distance before it goes downwards? My very crude drawing has the section-in-question in red. My thoughts are that if it goes south right after the trap, it almost resembles an S-trap, though the horizontal area may negate that problem - just want to know if it has to go for any minimum distance first.

 

[wwhitney]

The limitation is that the outlet of the trap has to be vented before it turns down or falls more than one pipe diameter. Via a dry vent or wet vent (common vent in the IPC parlance) or an AAV (for the IPC).

Cheers, Wayne

 

[Sponsor]

 

[Jim the dude]

I have a choice between using 1 1/2" or 2". Would using 2" solve the issue as it is self-venting? (not sure if that's the right term)

 

[Jim the dude]

The limitation is that the outlet of the trap has to be vented before it turns down or falls more than one pipe diameter. Via a dry vent or wet vent (common vent in the IPC parlance) or an AAV (for the IPC).

Cheers, Wayne

I have a choice between using 1 1/2" or 2". Would using 2" solve the issue as it is self-venting? (not sure if that's the right term)

 

[wwhitney]

No, self-venting is not a thing. Washer standpipes have to be 2" regardless.

Cheers, Wayne

 

[Jim the dude]

Actually, 1 1/2" is still allowed in the township I'm building this in, and the code officer allows it.

Since the pipes are on the outside of the wall, I'm just trying to do things in an aesthetically pleasing way as possible. Not to hijack my own thread, but could I put everything inside the wall and use an AAV? I'm not crazy about putting the trap in the wall but I could put an access panel in.

Obviously, the thing to do is to see what code wants and allows, just wanted to get some ideas on my options before I speak with them.

 

[John Gayewski]

You can put everything in the wall. The aav needs to be in a vented box. You don't need access to the trap. You'll have access to the drain through the aav opening (vented box) and the trap itself can be cleaned via the standpipe.

 

[Reach4]

Another alternative is to put the AAV under the sink before the wall. You need at least 2 pipe diameters of horizontal trap arm before the AAV. The AAV needs to stick up 4 inches.

So this would be on the red in your original post sketch.

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