dumping gray water in forest

First of all it depends on the rules and regulations where you are. In Colorado it is legal to dump grey water, just not in camp grounds. Grey water has been used for generations of farmers and ranchers for irrigation purposes. I use it on some property I own in Colorado for just that. Next one should look at where you are dumping. Ground that is already saturated or that holds water on the surface is not good for grey water dumping. Find some area that is porous or that drains well. Next, it is never legal or a good idea to dump black water in the forest or in a field. The concentration of waste should be drained in an appropriate location, ie dump station. You may have to drive a ways or use a buddy tank to dump your black water but that's why they make those devices. Finally, use a little common sense. Don't dump your grey water ten feet from someone's tent even if you aren't in a campground. Good manners makes good neighbors.