RVs capture grey water and black water in holding tanks, with grey water coming from sources other than the toilet.
The Boondocker's Bible has researched the legality of dumping grey water tanks on public lands. The U.S. Forest Service, National Park Service, Bureau of Reclamation, and Army Corps of Engineers all have regulations making it illegal to dump grey water on Federal lands. However, the Bureau of Land Management may allow the dumping of grey water in open public BLM spaces. State public lands may also ban the practice of dumping wastewater.
Dumping grey water from RVs is not considered good practice due to its potential to cause erosion, smell, and harm local wildlife. It can also attract animals and contain harmful chemicals, which can be harmful to plants, trees, and water sources.