If you have a recreational vessel with installed toilet facilities, it must have an operable MSD or holding tank on board. All installed devices must be U.S. Coast Guard–certified.

The types of MSDs are:

• A Type III MSD, the simplest and most common, consists of holding tanks or portable toilets. It requires only a small storage space and is simple to operate. Type III MSDs have the least effect on the environment since the waste is to be discharged on shore into a local sewage treatment facility.
• Type I and II MSDs are usually found on large vessels. Waste is treated with special chemicals to kill bacteria before the waste is discharged. Type I and II MSDs with "Y" valves that 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.

No Discharge Areas

It is illegal to disconnect, bypass, or operate an MSD so as to discharge sewage on inland waters or on coastal waters anywhere within the three-mile U.S. territorial limit.

• In designated No Discharge Areas:
  • No person may disconnect, bypass, or operate an MSD so as to potentially discharge sewage.
  • No person shall occupy or operate a vessel in which an MSD is installed unless the MSD is properly secured.
• The No Discharge Areas in California are:
  • El Dorado County: Lake Tahoe
  • Los Angeles County: Avalon Bay Harbor
  • Marin County: Richardson Bay
  • Orange County: Dana Point Harbor, Huntington Harbor, Newport Bay (Upper and Lower), Sunset Bay
  • Placer County: Lake Tahoe
  • San Diego County: Mission Bay, Oceanside Harbor, San Diego Bay
  • Ventura County: Channel Islands Harbor