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Discharge of Sewage and Waste

Water Pollution

Boaters appreciate the rich natural resources that abound throughout the waterways of Washington State. However, many people are unaware of the impact boating can have on these unique and treasured resources.

Water pollution problems associated with boating include discharges of oil, fuel, sewage, trash, fishing line, toxic cleaning and maintenance products, bottom paints, gray water, aquatic nuisance species, and aquatic invasive species. As a boater, it's your legal responsibility to help protect Washington's aquatic environment.

Sewage discharged from vessels can pose environmental problems, especially in shallow bays and inlets. Untreated sewage (even if it has been dosed with a deodorant product) MAY NOT be discharged into inland or coastal waters.

Proper Sewage Disposal

It is important that you treat or dispose of your sewage properly. If you have a vessel with installed toilet facilities, it must have an operable marine sanitation device (MSD) on board and be designed to prevent discharge into the water. If your vessel does not have installed toilet facilities, consider carrying a portable toilet.

  • All installed MSDs must be U.S. Coast Guard–certified.
  • Discharging treated sewage into coastal waters is permitted but discouraged. Avoid flushing your vessel's toilet in small bays, in marinas, and near shellfish beds.
  • Use pump-out stations. Find pump-out locations on the maps and at links on the Using Boat Sewage Pumpouts page. You also can visit or call 360-902-8555.

Types of MSDs

Types I and II MSDs

Types I and II MSDs treat waste with special chemicals to kill bacteria. When in waters where treated sewage cannot be dumped overboard (for example, any freshwater body of water), these MSDs must have the Y valve secured so that it cannot be opened. This can be done by placing a lock or non-reusable seal on the Y valve or by taking the handle off the Y valve in a closed position.


Type III MSDs provide no treatment and are either holding tanks or portable toilets. Collected waste must be taken ashore and disposed of in a pump-out or dump station or in an onshore toilet. Do not dump the waste in composting toilets on shore.

MSD Device

In any freshwater body of water, the Y valve must be secured.