it would help knowing the model you have and if you supplied pics of what you're talking about.
from what you describe, i agree with Ovair.
it sounds like a back flush device for the black water holding tank.
not sure if it was a factory option or if the previous owner had it installed.
if you look closely, you might find a brand name on it.
it's not for cleaning the toilet!
that would be one heck of a back flush device!
Dan-Retired California Firefighter/EMT
and Zoe the Wonder Dog(R.I.P.)
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package
4pt Equal-i-zer WDH and 1828lbs of payload capacity