Boating is all about water — both on the inside and the outside of a boat. The water outside a vessel mostly provides the pleasure part. Water in tanks aboard a boat, however, can be a tricky commodity to handle. 

If you are planning a one-day voyage on a small runabout, there may be only a fuel tank aboard, so dealing with freshwater or sewage holding tanks is not a concern. However, depending on the size of the boat, trip length, and number of passengers, it may be good to have a portable marine toilet (also called the head) available on board.  

On the other hand, those planning to charter a power cruiser or cruising sailboat for an extended voyage with several passengers have more to deal with, including drinking water quality and managing sewage holding tank odors and pump-out procedures. 

Depending on voyage length, holding tanks may have to be emptied, which has some manageable legal implications. Boat charterers should develop an understanding of the onboard water and sewage system operation and procedures for safely refilling water tanks and discharging sewage holding tanks. This knowledge will make a trip much more enjoyable by keeping onboard water flowing and holding tanks odor-free. 

The best source of information for learning how onboard water and sewage systems operate is to ask the boat owner or chartering firm representative. Consulting the owner’s manual is also a smart step to take, as well as understanding regulations governing sewage discharge at sea. 

Onboard Freshwater Tank Maintenance 

Most water quality issues are caused by algae, bacteria, or mold in tanks. These issues are easily resolved by using household chlorine bleach to disinfect the tanks. Water clarity, taste, and odor can largely depend on the source: water from a well, cistern, municipal treatment, or reverse osmosis system may retain some of its inherent qualities. Tips to keep in mind about freshwater tanks:   

  • As part of a pre-departure checklist, determine how long potable (drinkable) water has been in the tanks. Smell the water from a faucet and taste it using a clear tumbler.  
  • Determine the location of the freshwater tank, filing port(s), and pump equipment. Know the specific directions for refilling. Make absolutely certain that fuel is not pumped into the freshwater tank!       
  • Advise passengers about the importance of conserving potable water and using only what is needed during a voyage. 
  • Boiling water can remove water impurities and improve taste. Another option is to stow bottled water on board, but remember every bottle or container adds weight to the boat.  
  • If water quality degrades during a cruise, consider using household bleach (without perfumes, dyes, and other additives) to disinfect the tanks. The general rule is to add about one teaspoon of bleach for each 10 gallons of water. After adding the bleach, agitate the tank manually or take the boat for a short spin. Run faucets or other outlets to dissipate the bleach odor. 

Managing Onboard Sewage 

Efficiently managing human (commonly called black water) and non-human waste from other sources (gray water) is critical for boat operators, particularly on vessels that carry several passengers or during extended cruises. Operators are responsible for complying with raw sewage storage and holding tank pump out regulations.  

Sewage Discharge Laws

Raw sewage discharge from vessels operating in U.S. waters is regulated by federal and state laws. Boats with permanently installed toilets must be equipped with a Marine Sanitation Device (MSD) that either stores waste until transfer ashore or, if discharged, reduces the chloroform count to levels that do not pose a health hazard. 

Federal, state, and local marine law enforcement agencies actively monitor vessel compliance with sewage discharge regulations. Officers are trained to look for the obvious and not-so obvious signs of illegal discharge and are authorized to board vessels to check sewage system components. They pay particular attention to the sewage cut-off valve (commonly called the Y-valve), which is required equipment on boats with fixed sewage systems.   

Points to remember about sewage discharge laws:  

  • It is illegal to dump raw sewage inside a three-mile area extending from shore. Within that limit, sewage must be retained in a holding tank and transferred at a pump-out station. Outside the three-mile limit, sewage can be discharged, but only after on board treatment. 
  • Discharge laws vary from state to state. Some are “No Discharge” states, where it is illegal to discharge raw or treated sewage within all state waters, including inland lakes. 

Basic Tips for Sewage Systems and Holding Tanks

  • During the pre-departure briefing, familiarize passengers with head and sewage system operation, material not to be deposited in heads, and similar issues.  
  • Check the web or other sources when planning a trip to become familiar with any unique or special sewage dumping regulations along a planned route. 
  • Before getting underway, pay special attention to the sewage system cut-off valve (the Y-valve) and understand its purpose, conditions under which it can be open, and security seal issues. 
  • Check the location of holding tank through-hull ports, cut off valves, pump-out openings, tank level monitors, and electric switches that control sewage system components.  
  • Learn procedures and equipment for tank pump-out, and precautions for avoiding and controlling spills, electric shock, and effective ventilation. 
  • The easiest and most environmentally responsible way to discharge a full holding tank and avoid introducing sewage into waterways, even if in a legal area, is to plan intermediate stops at marinas with approved pump-out stations. 
  • Dispose of black and gray water, contaminated solids, and cleaning waste only at approved marina pump-out stations or landside treatment facilities. 
  • After each tank pumps out, have the tank rinsed and flushed to dilute residual sewage and reduce odor.

Planning ahead, practicing proper maintenance, understanding how onboard water and sewage systems work, and knowing the laws that cover sewage discharge from boats will make a voyage more pleasant voyage for all.