Most have a separate shut off valve somewhere near the base of the toilet. If you don't have one, you'll then have to turn off incoming water to rv and be sure the internal pump is also turned off. Then bleed off the pressure at a faucet before disconnecting the plumbing. You'll still get some drips when you first disconnect the toilet connection.
Fred & Vicki
Richmond Hill, Ga
2000 H.R.Endeavor/Freightliner/330 Cat