My 96 Challenger does the same thing. It sounds like i'm taking on water but there is no visible rise of water in the bilge. Weird, I don't know what it is
Ya , sounds like a old runny toilet.
Might be residule water left in the resonator trickle in the waterbox.
I know I need a new scupper , water comes in the cockpit from it, so I've been stuffing a wadded up piece of swim noodle foam in the hole under my seat , works till I get a new one I guess.