It is important to remember that it is illegal to discharge raw sewage from a vessel within U.S. territorial waters (the three mile limit). This includes the entire Chesapeake Bay, the coastal bays, and their tributaries.

Federal regulations regarding vessels with installed toilets have been in effect since 1980 and have been enforceable by the U.S. Coast guard. Effective July 1, 1997, a Maryland law (Natural Resources Article 8-741) allows the Natural Resources Police to enforce similar requirements. Violators are subject to a fine not to exceed $2,000.

When in Maryland waters:

• If a boat has an installed toilet, it must be equipped with a Coast Guard approved Marine Sanitation Devices (MSD).
• There are three types of MSDs. Type I and Type II MSDs are systems that treat the sewage to meet certain standards before discharging it into the water. A Type III MSD is a holding tank. Vessels 65' and under may have any of the three types. Vessels over 65' must have either a Type II or Type III.
• Type I and Type II MSDs must have a certification label affixed by the manufacturer. Type III MSDs do not need a certification label.
• If the vessel has a holding tank, all pathways for the overboard discharge of raw sewage must be blocked or secured by disconnection or physically blocking those onboard sewage lines of hull fittings.
• A "Y" valve is allowed; however, it must be secured to prevent the overboard discharge of raw sewage. Acceptable methods of securing the "Y" valve include the use of a non-reusable nylon tie (known as a wire tie), a padlock, or by removing the valve handle.
• For any vessel offered as a non-captained charter, the leasing entity must ensure that the vessel is in compliance with this law and include in the lease agreement, signed by the leasing party, a paragraph outlining the operator's responsibilities under the law.

The complete State Requirements for Recreational Vessels can be found here​.