Three broken lavs??? Sounds like a clogging issue. Time to break open the plumbing down below. We haven't had issues like this for a while, but we've had our share of clogged shtters. Sometimes its a fluke and we get lucky, other times, its ripping into the walls to get to the plumbing. They like to clog alot by this elbow just before going into the waste tanks. Sometimes gotta run a snake in there to loosen up crud. That's a Monday job. They like giving those to Monday boys. Oh, and tonight's my Monday. Hope that plane is in Beijing.