Always dump your black water first, then your gray! The gray will wash some of the yuck out of the hose.
Also, even if you're on full hookups, NEVER leave your black water dump valve open. Let the tank fill about half way then dump and close it back up. Otherwise you'll end up with a clog. Trust me. No fun.
Also, even if you're on full hookups, NEVER leave your black water dump valve open. Let the tank fill about half way then dump and close it back up. Otherwise you'll end up with a clog. Trust me. No fun.