Human sewage from boats creates environmental and human health problems, affects drinking water quality, recreational activities, reduces oxygen available to aquatic life, excess nutrients cause algal blooms (block sunlight penetration). Vessel sewage is more concentrated than domestic sewage because people on boats use less volumes of water for sanitary purposes than do people on land. A single boat discharging the contents of its holding tank into the waters of a harbor may pose little human health risk. However, if several hundred boats, on the other hand, are docked in a harbor with a poor flushing rate, and they dump their toilet wastes directly overboard, that can present a definite problem.


  • Always use shoreside restrooms when docked and before casting off.

  • Plan ahead for restroom stops.

  • Do not discharge sewage, treated or untreated, in any lake or reservoir.

  • Never discharge untreated sewage within 3 Miles from shore and within the navigable waters of the U.S.

  • Empty holding tanks at sewage pumpout facilities, or call a mobile pumpout service.

  • To find the locations of sewage pumpout facilities in California, go to,, or

  • All boats with installed toilets must have a Coast Guard-approved Marine Sanitation Device (MSD) if operating in U.S. navigational waters.

  • Boats without toilets – use a portable toilet on-board and empty at a dump station.

  • If you have a Y-valve with a through-hull fitting that allows direct overboard discharge, it must be secured in a closed position (using a padlock or non-releasable wire tie) when within the 3-mile limit.

  • Never discharge any sewage, treated or untreated, in a Federally designated “no-discharge area.” "No Discharges Areas" in California are:

    • Avalon Bay Harbor (Los Angeles County)
    • Dana Point Harbor (Orange County)
    • Lake Tahoe (Placer & El Dorado Counties)
    • Oceanside Harbor (San Diego County)
    • San Diego Bay (San Diego County)
    • Upper and Lower Newport Bay (Orange County)
    • Channel island Harbor (Ventura County)
    • Huntington Harbor (Orange County)
    • Mission Bay (San Diego County)
    • Richardson Bay (Marin County)
    • Sunset Bay (Orange County)

  • Avoid holding tank disinfectants and deodorizers that contain chlorine, formaldehyde, or other components that can be harmful to aquatic organisms. Whatever you use, follow instructions carefully and use the recommended amount for treatment.

  • Choose MSDs that use a holding tank or use a portable toilet. When regularly emptied at a pumpout or dump-station, they offer the best environmental protection.


Learn how to properly operate a sewage pumpout.
Watch this video from the San Francisco Estuary Partnership and learn how to use a pumpout properly.

Trying to solve a smelly problem?  Learn more about Green Solutions for Smelly Problems.

  • Empty your holding tank on a regular basis. Full and overfull tanks are difficult and dangerous to drain. Keep a pumpout log on your boat to keep track of your holding tank capacity.
  • Periodically rinse the entire system with water. Connect a hose to the deck fitting for the holding tank and fill the tank with fresh water. Use the pumpout to pump the water out. Repeat if necessary.
  • Use enzyme and bio-active treatments, when possible, as these are biodegradable and less toxic treatments.
  • Before you add any holding tank treatment, use a vinegar solution, about once a month, immediately after a tank has been emptied. This solution will help to reduce scale buildup and it will keep the walls of the hose clean. Without buildup on the walls, hoses last much longer and are not so easily permeated by bad smells.
  • Do not use treatments that contain any components that can be harmful to aquatic organisms. Avoid chemical treatments that contain chlorine compounds like sodium hypochlorite, formaldehyde, para-formaldehyde, ammonium compounds, bronopol, glutaraldehyde, para-dichlorobenzene, Dowicil, and other caustic chemicals.
  • To clean the boat’s head, use a mix of one half cup borax per one gallon of water and sprinkle baking soda around the rim.
  • Over time, the system hoses, made up of a rubbery material, start absorbing the sewage smell. Perform the following quick test:

    Use a rag with hot water and put it around the hoses for few minutes. Remove the rag and if the rag has a bad odor, like of sewage, the odor is permeating though the hose and it's time to change the hose.

Learn more about Sewage Holding Tank Systems for Recreational Boats.

Learn more about boat–to-boat mobile services.

Learn more about environmental laws associated with sewage.

Information on Boat Sanitation System Installation and Repair Services.

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