Montana law states that it is illegal to discharge any garbage, refuse, waste, or sewage into or near the water. If you have a recreational vessel with installed toilet facilities, it must have on board an operable marine sanitation device (MSD) that is self-contained and incapable of discharging directly into the water.
There are three types of MSDs.
- Types I and II MSDs are usually found on large vessels. Waste is treated with special chemicals to kill bacteria before the waste is discharged. Types I and II MSDs with Y valves that would direct the waste overboard must be secured so that the valve 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.
- Type III MSDs provide no treatment and are either holding tanks or portable toilets. Collected waste should be taken ashore and disposed of in a pump-out station or onshore toilet.
Vessels 65 feet or less in length may use a Type I, II, or III MSD. Vessels more than 65 feet in length must install a Type II or III MSD.
All installed devices must be USCG–certified.