I have a stacking W/D next to a laundry tub and the 2 share a 1 1/2" drain and supply. I cut into the ABS and installed a WYE that directed the water down and away from the sink drain. Then another WYE on top of the first WYE. On the top of this WYE I put a cheater vent. Out the side of the WYE I put an adapter that allowed me to screw in a hose barb. The Laundry drain hose clamps to the host barb and the water goes down the drain 100%. I hope this isn't too confusing. I could draw it better than explain it.