Local campgrounds often have dump stations that you can use free of charge. In other cases you may need to find a local RV park and pay a nominal fee to dump. State parks are usually a good place to find facilities but usually you have to pay a "day use" fee for the privilege but this is seldom more than a buck or two. As a last resort we might have to travel to a nearby municipality and use facilities at their sewage plant but these instances are quite rare for me.