What Type of Marine Toilet is Right for You?

Choosing the right sewage management system for your boat depends on several factors, including if the law requires you to have a specific type of Marine Sanitation Device. When considering your options, familiarize yourself with the Laws and Regulations and ask yourself the following:

  • How often do you use your boat?
  • How long are the trips you take?
  • What type of waterways do you boat on?
  • How many people are usually onboard and how old are they?
  • Do you or anyone you bring onboard have health conditions that should be taken into consideration?
  • Do you have the time, funds, and know-how needed to properly install, operate, and maintain the system you’re considering?

This guide will help you explore the different sewage management options.  Keep reading to learn more about each system.

Installed Toilet

Vessels with an installed toilet must have an operable US Coast Guard certified Marine Sanitation Device (MSD). There are three types of MSDs.

Type ITreatment devise- uses maceration and disinfectants such as chlorineSewage bacteria count is reduced to less than 1,000 per 100 milliliters, and there are no visible floating solidsFor vessels 65 feet or less
Type IITreatment devise- uses bacteria to break down the solid waste followed by disinfectionSewage bacteria count is reduced to less than 200 per 100 milliliters, and suspended solids are no more than 150 milligrams per liter.For vessels of any size
Type IIIHolding tank- stores untreated sewage onboardCannot be discharged in state watersFor vessels of any size

These systems can vary greatly. Systems can allow for emptying the holding tank only through a pumpout via the deck waste fitting or can include an option for overboard discharge before or after the holding tank or both. Additionally, type III MSDs can be combined with a Type I or Type II MSD.

The Y-valve is part of the MSD system, found on vessels with a type III MSD (holding tank). Depending on your system the Y-vale directs waste to a deck waste fitting for pumpout, to the holding tank, or overboard. Keep your Y-valve in the closed position to prevent overboard discharge.

Installed toilets tend to be a bit more complicated, require regular maintenance, pumpouts, and the occasional repair. However, they are also considered the most comfortable, easy to use, and are standard on larger vessels.


  • Easy to use- most similar to your home toilet
  • Comfortable
  • Standard on larger vessels


  • Complicated, there are many different systems, different configurations, and they require substantially more plumbing than other options
  • Require regular maintenance
  • Need to pumpout to properly dispose of waste
  • Needs occasional repairs

Keep your Y-valve in the closed position to prevent overboard discharge.

outreach educator demonstrates how to empty a portable toilet into a dump station for boaters

Photo by Vanessa Cholewczynski, Oregon Sea Grant

Portable Toilets

These are a simple, convenient, and less expensive sewage management option that require minimal space. Due to their simple design, there is little maintenance, and it is unlikely to need repairs, saving both time and money. However, they have a limited capacity for waste so are not ideal for long trips with multiple people. Additionally, emptying a portable toilet has more of a ‘yuck’ factor since it’s not a closed system. Portable toilets should be emptied and rinsed at a designated dump station. Alternatively, they can be emptied via a suction wand at a pumpout facility, or into any landside restroom.


  • Simple design
  • Requires little maintenance saving you time and money
  • Easy to use


  • Limited waste capacity
  • Higher ‘yuck’ factor to empty
Marine Composting Toilets

Although not as common, the number of boaters opting for a marine composting toilet is on the rise. These systems are a Type III MSD and considered certified by the US Coast Guard if they meet the following requirement:

  1. “It is used solely for the storage of sewage and flushwater at ambient air pressure and temperature” and,
  2. “Be designed to prevent the overboard discharge of treated or untreated sewage or any waste derived from sewage (Type III).”

Most composting toilets have not been examined by the US Coast Guard. Manufacturers attest that the device meets the above requirement.

Marine composting toilets are designed to separate liquids from solids. Liquids are diverted to a removable tank for storage and then proper disposal at a sewage dump station or in any landside restroom. Solids sit in a removed chamber with a handle and are mixed with sawdust, peat moss, or coconut husk fibers. Bacteria in the solids chamber breakdown waste and leave behind a black odor-free powder, which can be disposed of in the trash.

Marine composting toilets are easy to clean and have less offensive odors then conventional boat toilets since the solids and liquids don’t mix, you don’t get that typical sewage smell. Their simple design means less time and money spent on installation, maintenance, and repairs. They’re also lighter in weight than conventional installed toilets.

However, marine composting toilets aren’t for everyone. They are taller than most conventional toilets, which might make them tricky to install or use. Maintaining a semi-dry environment in the solids chamber is important and can take some practice for users. Some models include a vent fan to circulate air in the solids chamber, so electricity usage may increase. Other’s just have air vent holes with screens, it’s important to check the screens regularly for tears to keep bugs out of the chamber.


  • Easy to clean
  • Not as smelly as conventional boat toilets
  • Simple design
  • Requires little maintenance saving you time and money
  • Lighter in weight than conventional boat toilets


  • Taller than conventional boat toilets
  • Vent fan may increase electricity usage
  • User practice needed to keep liquids separate from solids
A Bucket

Although not the most glamorous of options, a bucket is good for ‘emergency’ needs especially when taking short trips with younger children. Just make sure you have a secure lid for it. You can empty the bucket at a designated dump station, into any landside restroom, or via a suction wand at a pumpout facility. Human waste in a bucket is untreated and it is illegal to discharged it overboard within state waters.


  • Simplest design
  • Least expensive


  • Higher ‘yuck’ factor to empty
  • Not comfortable
  • May be difficult to use

I hope you found this information useful as you consider what type of marine toilet is right for you. I’d also recommend talking with several other experienced boaters about their system, if you can find a boater with the same system you’re considering installing that’s even better. Anchors aweigh!