Uggg, that sounds nasty.
Regarding go-no-go Captains call in conjunction with maintenance control and the Minimum Equipment List (MEL). While it's not a safety issue it sure the heck is a convenience issue. I guess I would rather get to YYZ verses a hugh delay or even a cancellation since I would normally have a connection to meet.
It seems there are lots of issues with the Lav's these days, not sure why but you see write-ups on the Aviation blogs for frequently than previous.