There are folks who when arguing weights insist that they only tow with empty tanks. I guess they always stay at RV parks/resorts with full hook ups. Most of the campgrounds we visit don't have dump stations and even if they do that doesn't necessarily mean they are available. I have seen the line at Zion stretch back a dozen rigs, as in a couple of hours and not everyone can or will wait that long. Broken dump stations are not unheard of either.
My grey or black tanks are at the rear of the trailer and if they are more than half full I need to compensate by adding at least half a tank of fresh as that tank is all the way forward to maintain the proper TW. As all three are 30 gallons just half a tank each can easily add 400+# to the drive home, usually down some serious mountains at least until I can find a dump station at another CG or truck stop. Just another reason to understand and utilize GVWR's when computing actual loads. :C
