If you're at a full hookup campsite, do
NOT leave the black tank valve open. Leave it closed until the tank is at least half full, if not three quarters, to avoid the solids build up you experienced. Also, use plenty of water when flushing.
Dutch
2001 GBM Landau 34' Class A
F53 chassis, Triton V10, TST TPMS
Bigfoot Automatic Leveling System
2011 Toyota RAV4 4WD/Remco pump
ReadyBrute Elite tow bar/Blue Ox baseplate