I wish I had discovered this forum earlier...

I moved my washer/dryer upstairs and had no trouble doing the plumbing, I thought :-)

It is working fine so far, but after reading some posts it seems I may should have vented the washer drain.

Currently it is on a 40" stack pipe. The P-trap is below the floor, and the drain line tee's into the sink's 1.5" drain eight feet from the washer's P-trap. Then the sink drain empties into a 6" drain about 12 feet later.

So far no problems... I have not yet done the drywall behind the washer completely. Should I add a Studer AAV? The washer drain is not a tight fit, so I assume some natural venting is occurring, right?

Thanks in advance!

That non-tight fit isn't going to help as much as you think. The vent should be after thetrap. A stuer vent would be a good option. Are you saying the sink drain isn't vented either? If it has a trap it should have a vent.

The sink is vented... all seems to be working fine... I was just wandering if the washer drain had to be vented or if the vent from the sink was OK. Thanks.

If the washing machine trap is not vented and not on a 3" trunk line then the flow of water could pull the trap dry.

Thanks Doug... that I understand (now). I could not understand why the vent went after the trap... duh... now I get it. I have had no problems doing 4 loads a day for 2 weeks now. SO I think the vent from the sink is sufficient, but if I have a problem I will have to put in a second trap + AAV after it or cut the flooring to access it. (The drywall is nearly finished in the basement!)

Thanks everyone!

I am a photographer. Guess I should go over some posts related to that and return the favor ;-)