What should you do to prevent the discharge of untreated waste from a Type I or Type II marine sanitation device (MSD)?

To prevent the discharge of untreated waste from a Type I or Type II marine sanitation device (MSD), securing the Y valve so that it cannot be opened is essential. This is because the Y valve controls whether the waste from the MSD is discharged into the water or retained in the holding tank. If the Y valve can be opened, it poses a risk of discharging untreated sewage into the water, which is harmful to the environment and violates boating regulations.

By ensuring that the Y valve is secured and cannot be accidentally opened, boaters comply with environmental protections and promote safe sanitation practices. This action directly addresses the primary concern of preventing untreated waste from entering the waterway, contributing to cleaner and safer aquatic ecosystems.

Other options do not directly address the risk of discharge. Checking the discharge regularly is important, but it does not prevent the action itself. Replacing the MSD annually ensures that the device functions correctly but does not specifically prevent discharge during the year. Flushing the MSD with freshwater is a maintenance step but does not contain or secure the waste, which is crucial in preventing untreated discharge.