Run hose to roof vent; chase lav drain plug-up all the way to last corner, clean-out before the large exit pipe. Ergo -

Mother's Day gift given:
new sludge for the white-worm beasties roiling in the tank
(previously caught in a memorable Indie film I retained,) entitled:

My Earliest Life as a Repo child, with cohorts





Small Hallmark Card flushed along, When you care enough to send the very beast.