When in SeaTac, Washington, you have several options for dumping your RV's black water and gray water tanks. The KOA - Seattle / Tacoma KOA Campground offers a convenient dumping station for RV travelers. Another option is the Elks Lodge, which provides a dump station as well as fresh water and a hose for flushing tanks.If you're looking to enjoy some outdoor recreation, Saltwater State Park has a dump station available for use. Additionally, Bryn Mawr Beach & RV Park offers an RV trash bin and waste disposal facilities for your convenience.