The negative effects of boat sewage in the environment are just as, if not more, impactful than those from other sources of boat pollution. In fact, a single toilet flush of untreated sewage from your boat can cause the same environmental impact as 10,000 flushes from your home toilet, where waste is processed by a sewage treatment facility (San Francisco Regional Water Quality Control Board)! Raw sewage contains excess nutrients that contribute to harmful algal blooms, use up valuable dissolved oxygen, and contaminate shellfish beds with pathogens.

 Sewage by BayGreen

  Photo by: BayGreen

Raw sewage takes oxygen to decompose sewage in water. The amount of dissolved oxygen in the water required to decompose organic matter is measured in terms of “Biological Oxygen Demand” or “BOD”. Although the volume of waste from a boater is small, it is concentrated, which increases BOD. High BODs are often found in marinas and poorly flushed areas. Excess phosphorus and nitrogen from sewage can also contribute to harmful algae blooms (HABs), which block sunlight penetration and contribute to lower oxygen levels. High BODs and HABs make it difficult for fish and other aquatic life to survive.

Raw sewage contaminates waterways with harmful pathogens like bacteria, viruses, and parasites. These pathogens can cause symptoms ranging from nausea, upset stomach, respiratory problems, skin infections, and more. Encountering polluted water or consuming shellfish contaminated by raw sewage can also cause more serious water-borne diseases. In addition, floating sewage in recreational waterways is disgusting. It takes away from our enjoyment on the water, impacting recreational activities and our economy.

  • Always use shoreside restrooms when docked and before casting off.
  • Plan ahead for restroom stops.
  • Install an onboard head (toilet) with a US Coast Guard approved Marine Sanitation Device (MSD).

There are three different types of MSDs that can be certified by the U.S. Coast Guard to meet the requirements in 33 CFR Part 159.53, each having its own design, certification, and discharge criteria. 

  • Type I is a flow through discharge device that produces effluent having a fecal coliform bacteria count not greater than 1,000 per 100 milliliters and no visible floating solids.  This type of device is typically a physical/chemical-based system that relies on maceration and chlorination.  Type I MSDs are issued a Certificate of Approval. 
  • Type II is a flow through discharge device that produces effluent having a fecal coliform bacteria count not greater than 200 per 100 milliliters and suspended solids not greater than 150 milligrams per liter.  This type of device is typically a biological or aerobic digestion-based system. 
  • Type III is a device that prevents the overboard discharge of treated or untreated sewage or any waste derived from sewage.  This type of device is typically a holding tank and may include other types of technology including incineration, recirculation, and composting.

Make sure that your Type I or II MSD meets Coast Guard requirements by looking for a certification label. A Type III MSD is not required to have a label if it simply stores sewage at ambient pressure and temperature.

Not all marine sanitation devices (MSDs) require the use of chemicals for day-to-day operation. Many chemical disinfectants and deodorizers used in MSDs contain dangerous chemicals. Chlorine compounds (including sodium hypochlorite), formaldehyde, para-formaldehyde, ammonium compounds, glutaraldehyde, para-dichlorobenzene, or antimicrobials (such as Dowicil or Bronopol) are harmful to aquatic life. It only takes one-tenth of a part per million of chlorine to hurt or kill aquatic organisms.

Use enzyme and bio-active treatments when possible as these are biodegradable and less toxic. Read labels carefully and use only the recommended amount. See the Green Solutions section (below Question 3) for more tips.

 o   Know your on-board system  

o   Know your laws 

  • Discharging raw sewage into California’s lakes, rivers, reservoirs, or coastal waters within three miles of shore is prohibited within U.S. navigable waters. Fines of up to $2,000 can be imposed for illegal discharges.
  • State law also prohibits dumping any treated or untreated human waste in a marina, yacht harbor, freshwater lake, reservoir, or freshwater impoundment, No Discharge Zone, and river that doesn’t support interstate traffic.
  • It’s illegal to discharge untreated sewage into a Sanctuary and it’s generally illegal to discharge treated sewage (from MSD Type I and II) if you have sufficient holding tank capacity. If you operate in these waters, your Type I or II MSD must be connected to a holding tank or secured to prevent all sewage discharges. Some harbors and marinas also have local ordinances preventing the discharge of other wastes, such as greywater. If unsure, check with the marina manager or harbor master for a complete list of local ordinances


  • 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 & 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)

pump it, dont dump it imageo   Pump It, Don’t Dump it!
Look for the national pumpout symbol that marks the location of a pumpout facility. For instructions, watch this video, follow these instructions or ask a marina manager/staff for help. Pumpout only your holding tank. Pumpouts are not designed to handle bilge water, solid material, or other substances.




y valve imageo   Keep your Y-Valve properly secured in a closed position to prevent accidental discharges (use a padlock or wire tie). Watch this video to learn how to properly secure your Y-valve to prevent an accidental discharge.




pump outo   To identify the nearest participating pumpout, dump stations and floating restrooms,  visit: dbw.parks.ca.gov/pumpouts  or download the free Pumpout Nav app from your Android or Apple devise. 


o   Do not want to deal with sewage? If you don't want to service the holding tank yourself, consider using a mobile pumpout service.


Report sewage discharges to the National Response Center (800) 424-8802 and the California Office of Emergency Response (800) (645-7911)

  • 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.
  • Clean with a vinegar solution. 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.
  • Deodorize with borax and baking soda. To clean and deodorize the boat's head, use a mix of 1/2 cup borax per 1 gallon of water. Clean frequently with a solution of baking soda and water, and sprinkle baking soda around the rim.
  • Change the hoses when needed. Over time, the system hoses, made up of a rubbery material, start absorbing the sewage smell. Perform the following quick test: Wet a rag with hot water and put it around the hoses for a few minutes. Remove the rag and if the rag has a bad odor, like sewage, the odor is permeating through the hose and it's time to change it.

Download the Pumpout Nav app.

The Pumpout Nav App Video

How to Use a Sewage Pumpout Video 


Check out these Educational Resources, Videos, and Much More