Lisa spent time this afternoon getting the washing machine leveled and connected to the water lines the plumber cleared up yesterday. Then she started a null load: no laundry, no soap, just cold water and high water level, just to make sure everything worked. The first cycle seemed to go okay, but then it began the rinse cycle and we heard the very unwanted sound of water splashing onto the floor. Lisa ran back and unplugged the washer. The drainpipe is plugged! When the washer started to vent, it backed up the drain pipe and started flooding the laundry area floor.
We mopped up the water — since it was just plain water, it wasn't particularly messy, just wet — and vented the remaining water from the washing machine into an empty plastic trash can, which I relayed (it took several trips) to the adjacent bathroom and poured down the toilet. At least the toilet drains properly. We'll have to call the plumber and have him back in next week so he can fix the laundry drain as well. We were both surprised that this hadn't been tested earlier.
I guess we're not yet rid of having to take our dirty clothes to the laundromat.