The travel trailer has sprung a leak in one of the two drain tanks. When Lisa first noticed it, she opened the drain valves to reduce the load on the system. A day later, even after the tanks drained, putting any water down the bathroom sink (nothing else) causes a small leak under the trailer. This could be very tricky to fix. To reduce mess, we got a bucket, lined it with a heavy plastic bag, and put a layer of sorbent (we got a bag of the oil-cleanup stuff from Lowe's) in the bag to catch the small amount of drippage. We've called a mobile RV repair guy (suggested by the local tow company from who we buy our propane) who will be here tomorrow morning to try and diagnose the problem. Lisa thinks that a pipe may have come lose from the bathroom sink drain into the holding tank. The problem is that there's no simple way to get at that connection, given how tight everything is constructed in a travel trailer.
If we have to haul the trailer to a shop for heavy repairs (which replacing a holding tank might be), it would be very difficult, given that we're living out of the trailer and depending upon it for our hot water and cooking.