Asked Ranger if I washed dishes in my sink then drained the gray water into bucket and used his drain if that was OK. His answer was "Anything" drained out of an RV is considered "black water...
In Montana, in USFS campgrounds and State Parks, it is against the rules to: 1. Dump grey water on the ground (yes, tenters can get away with scattering it in the brush.) 2. Empty RV tanks into the vault toilets. Keep in mind that there usually is no dump station.