This happened to me once in my own classroom. My drain backed up. It was very
gross. Took weeks before the custodian could repair it. They claimed the pipes
ran uphill and that's why it always backed up. They said it would take time for
the reapairs. So I decided to haul water from the cafeteria sinks. I kept a
few buckets for dirty paint brushes and trays. After school I would wash them in
the cafeteria sinks. The cafeteria manager hated it. (I expected that). And
griped louder than I did. My sink was fixed the next day.