Customer described water dripping down their wall, behind the laundry machine. The drain is 1 1/2”. It appears to have a shorter than necessary riser and possibly little to no fall on the drain line. Everything is in ceilings or walls and can’t be seen. We weren’t able to recreate a leak. It looks like when the drain is overwhelmed, it will back up. I recommend repiping the drain line and installing a new washer box with a properly plumbed drain. Estimate for replacing the existing laundry drain would be 2500-3500 without any demo work.