How to tie washer drain into horizontal drain from sink

[econjon]

I would like to move my washer to a wall that has a 2" drain running horizontally (from laundry sink/vent approx 3' away). The drain line is approx 8" above ff. I am wondering if it is ok to use sink vent stack? And if so, what fitting should I use to tie the p trap arm in?

The blue tape to the left is where vent stack is.

 

[Mr tee]

The washing machine needs a vent between the trap and the horizontal drain line.

 

[Sponsor]

 

[econjon]

I was wrongly under the impression that it would be ok as a wet vent. But is the new vent to avoid the washer siphoning the sink trap? The drain is sloped down to right if that makes a difference.

I’d like to avoid pulling drywall behind the counter to tie in a new vent. Are AAV ok for a washer?

 

[wwhitney]

You're in California, where the state plumbing code is based on the UPC. AAVs are not allowed. And wet venting is only for bathroom groups, not for laundry sinks or clothes washers.

So what you likely want to do is pull off the drywall to the right of the counter to add a laundry box. The standpipe can go to a trap above the horizontal drain (max 18" AFF), then to a san-tee for venting. The bottom outlet of the san-tee (drain) will join the horizontal drain using a combo.

The top outlet of the san-tee (vent) will rise to at least 6" above the standpipe, then it can go to the left to join the sink vent. You might be able to do it within the vertical space between the upper and lower cabinets. But I think you might be better off taking down the one upper cabinet (likely easy to do) and running the vent higher up.

Cheers, Wayne