Usually, all the tanks count against you. Biggest reason most people don't carry much more than enough water in the fresh water tank to flush the toilet, then the little bit that's in the black tank. Keep the gray tanks empty. We were so close to gross weight on our fifth wheel, we actually dump the water heater, as that saves us just under 100 lbs.
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.