Selecting A New Marine Toilet / Head (Complete How-To Guide)

Selective photo of a white boat toilet with the seat in the up position

We can all agree that space, power and water are all major factors in our boats. Which is why selecting a new marine toilet is a crucial decision. No one wants to flush their hard-earned money down the drain. For many boaters it’s daunting trying to figure out which is the right one to choose. To help you I wrote this how-to guide for selecting a new marine toilet.

This article covers toilets types, common installations, maintenance and marine sanitation laws. By the end, you will learn everything you need to know to pick the right marine head for your vessel.

Want to skip to a particular section? Feel free to click the navigable table of contents to do so. Alright, let’s get started.

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Related: Top Electric Marine Toilets In 2023

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Table of Contents

What Is A Marine Toilet?

A marine toilet or “head“, is a special type of toilet that allows for sanitary conditions out at sea. Its operation is the opposite of a traditional toilet you find on land. A traditional toilet is a terrible idea for a boat. This is because the water would spill from the toilet bowl as the boat rocks. To fix potential spillage a marine toilets’ bowl stays dry until its in use. In it is in use a pump pushes water into the bowl to facilitate sanitation.

Current marine toilets come in a variety of types, sizes and shapes. Plus there are many variations of water sources, controls, and flush controls available.

Marine Laws For Selecting A New Marine Toilet

Next, it’s important to understand the basics of marine sanitation laws. Marine sanitation laws differ slightly for boats operating in Canadian or US waters.

In both US/Canada, vessels with permanent installed toilets must use a Marine Sanitation Device (MSD) onboard. The MSD has to either store waste until it’s transferred ashore. Or reduce coliform counts to a low level to discharge into waters without posing a health hazard.


3 Types Of Marine Sanitation Devices or MSDs:

  • Type I MSDs discharge chemical treated effluent. With a fecal coliform bacterial count not greater than 1000 per 100 milliliters of water. No visible floating solids.
  • Type II MSDs discharge chemical treated effluent. Having a fecal coliform bacterial count of less than 200 per 100 milliliters. As well as, suspended solids not greater than 150 milligrams per liter.
  • Type III MSDs are devices designed to store sewage until it’s pumped out at a pump-out facility. Or discharged outside the boundary of three miles from shore. Known as “holding tanks”.

To help you decide on the best MSD for your vessel it’s vital to consider where you will discharge sewage.


Marine Sanitation Laws For Discharging Sewage:

Below are the marine laws you must follow to properly dispose of raw sewage on your vessel:

  • Boating over three miles from a coastline. In this area it’s legal to discharge raw (untreated) waste overboard. You can do this either by emptying direct from the toilet or from a holding tank. I prefer a dual system design that allows dockside pump-outs and discharging offshore.
  • Operating inside the three–mile limit to a coastline. Here it’s illegal to dump raw sewage unless it’s treated by an onboard treatment device. Such as a Raritan Electro Scan (Type I or II MSD). This uses electricity to create chlorine from saltwater which disinfects the raw sewage.

photo of a type 1 MSD called the raritan electroscan marine sanitation device 

* Note: USCG approved Type I Marine Sanitation Devices (MSDs) are not legal in Canada. An example of a popular Type I MSD is the Raritan. Yet, type II MSDs are legal in Canada, except in designated sewage areas as defined in the Regulations.

  • No Discharge Zones (NDZ) are all non-navigable inland freshwater lakes and Great Lakes. Overboard discharge in NDZs like in a reservoir are illegal and subject to fines. Whereas any navigable interstate waterways (except special NDZ zones) allow for treated discharge.

photo of a sunny landscape with concrete reservoir blocking green water

If you use a Y-valve (common in saltwater) in your sanitation system, be aware that some waters have special rules. These areas will require a special locking mechanism for the Y-valve. This mechanism will lock the valve and flow toward the holding tank.

More and more coastal areas are becoming NDZs. Like in Michigan, New Mexico, Rhode Island and Vermont where all waters are now, no discharge zones. Making the case for dual sanitation systems to ensure versatility throughout the US.

Five Types Of Marine Heads

For most vessels there are four distinct types of marine heads. Each with a different method of flushing away the waste. These are the common types of boat heads:

  • Porta-Potty (Portable Boat Toilet)*
  • Manual Pump Head
  • Electric Head
  • Vacuflush Head
  • Composting Marine Toilet

* In some jurisdictions, for power boats a Porta-Potty doesn’t qualify as a marine head.



A Porta-Potty, sometimes called a cassette toilet is the most basic head installation to deal with onboard sewage. This type is common for smaller vessels that don’t have the space for a full sanitation system. It has both a refillable water supply and holding tank incorporated into the actual head. There is no permanent plumbing system in a portable toilet system, the head does all the work with a caveat.

diagram of a marine porta-potty with label showing lower waste storage tank

To operate it, you do your business, then actuate a hand/foot-operated pump. This both pumps water into the bowl and opens a trap door system that lets waste fall into the lower holding tank.

Advantages for this type are the space it saves, it’s near impossible to clog and the low initial cost. Plus if you add a chemical deodorizer to the holding tank, it’s virtually odorless.

The caveat for a portable toilet is when the holding tank is full. It’s not an enjoyable experience to have to remove the tank on shore and dump the holding tank.


Manual Pump Head

The manual pump head abandons portability as it uses a permanent plumbing system. This type of head uses a pump, hoses, valves and a larger holding tank to store waste. I’ll further explain waste storage options later in the article. Using an installed holding tank means you need to empty waste at a marina’s pump-out facility. This is more civilized than hand emptying a Porta-Potty tank.

isolated image of a manual pump boat toilet

A manual pump head like a Jabsco, consists of the bowl, a hand-pumped raw-water intake, and a discharge hose. The output hose flows to the holding tank, then flows to either a pump-out hose or self-discharge hose. Depending on your waste storage system, there might be a macerator too. This chops up waste to smaller bits to reduce clogs in the waste hoses.

To use it, once you make a deposit, you move the pump up and down by hand around a half dozen times. On the up stroke of the hand pump, the system draws water into the bowl. Next, on the down stroke the system pushes the waste out through the discharge hose.

The big advantages of this head is that it’s repairable, easy to maintain and quiet to use. Another great function of this type of head is the ability to switch to either wet or dry flushes. A dry flush is when you set the switch to not allow fresh water to enter while pumping. Dry flushing is for fluid only waste, to help reduce the volume of liquid filling the waste holding tank. Which is a genuine concern for boats with a small holding tank on board.

Shopping Considerations For A Manual Marine Head

  • Direction Of Pump Handle Throw. A horizontal throw (back and forth) tends to be less tiring than a vertical throw (up and down). Expect horizontal throw pump handles to cost more than vertical throw versions.
  • Seat Height & Sturdiness. Ensure the height of the seat is at a comfortable height for yourself. Next pay attention to the material durability of the seat and its hardware. Using the head in rough waters puts stress on the seat hinges. So look for beefy hardware that won’t snap and dump you off the seat before you finish.
  • Larger Joker Valve. This rubber valve is what the waste passes through during each hand throw of the pump lever. A bigger valve size means a lower chance of clogging. Bear in mind, a faulty joker valve can permit water leakage into the sink in rough water. Keep a close eye on the component.
  • Ability To Rebuild Toilet. Marine toilets tend to need rebuilding every couple of years depending on amount of use. Look for brands that offer quality rebuild kits and instructions.
  • Toilet Weight. If you are upgrading from a Porta-Potty it’s important to know that a manual head will add about 22 pounds (9.98 kg) of weight.


Electric Head

An electric head is an improvement of a manual head because it replaces the need to hand pump the flush. You either replace the manual head with and electric model or upgrade the existing head. To do so you need to add an electric pump, flush switch and a 12 volt circuit to the compatible system.

Isolated photo of a Jabsco Electric Marine Toilet

This design uses an electric pump to create suction to pull in water and push waste out from the bowl. Inside the pump contains a macerating function that grinds up waste and paper. Which reduces clogging of the output hose to the holding tank or overboard, if you are offshore.

Power consumption of an electric head is low due to the quick speed of the flush, as most finish in under 30 seconds. Yet, the toilet will use a brief load burst of between 20 and 30 amps. Thus, you should consider adding a separate circuit breaker for an electric head.

To operate this type, a user only has to engage a button for the duration of the flush. For guests that aren’t used to marine sanitation this type of boat toilet is great.

Keep in mind that this design is quite noisy during a flush. Due to the sounds from the electric macerator and pump. So night flushes may annoy guests sleeping next to the bathroom. Another consideration when shopping for this type of head is access to the moving parts. This head does need maintenance, if the moving parts aren’t accessible expect headaches. The biggest issue though, is if the boat losses power the toilet pump motor losses flush function.


Vacuflush Head

What is a Vacuflush head? As it’s name suggests, a Vacuflush uses an electric vacuum pump to keep a constant vacuum on the waste line. It uses a freshwater input to cut odor and calcification build-up in hoses. Calcification can happen due to lake and seawater organisms that die in the hoses. This head also uses very little water for operation compared to the 0.75 gallon (2.84 liters) the manual or electric heads use. Plus it uses much less power consumption at 3-7 amps whereas electric uses about 10-15 amps.

diagram of a vacuflush marine toilet with foot pedal labelled

How Does A Vacuflush System Work?

1. Vacuum is constant in the system at all times. Before sitting down, you need to add water in the bowl. Most need you to raise the foot pedal or lever to do this.

2. Sit down and do your business. You flush by pressing down on the pedal/lever. This will release the vacuum pressure stored by the system. This change in pressure inside the vacuum tank activates the vacuum pump. Resulting in the bowl clearing in an instant moving waste through the vacuum pump. Pushing it at high speed through the output pipes to the holding tank.

3. Once you release the flush pedal/lever, you recreate a vacuum tight seal. The vacuum pump continues to run (its noisy) until recharging the vacuum level in the system. Recharging takes about one minute, depending on how long you held the flush.

A Vacuflush marine head is typical for larger power yachts for many years. They work well but are very expensive to retro fit and repair compared to the other types.


Composting Head

The composting head is a bit of a newcomer to the marine-toilet market. Two important install considerations for this type are the footprint and bulkhead clearances. If you have the room though with this type there are no hoses or holding tank need either.

diagram of a composting boat toilet with removable storage tank labeled

Another benefit over other systems is it doesn’t need seacocks or through-hulls. The waste system works by separating the solid and liquid waste. Inside it channels liquid waste into a single tank and solids into a composting tank. In a typical design there are two small holes in the front of the bowl for liquids. Then a large center hole for solids. Both tanks sit under the head to save space in the hull, which is the other big bonus of this style of boat toilet.

Composting Toilet Operation

To use this type of head it’s best to do your liquid or solid business sitting down. Expelling liquids sitting down is to ensure you hit the small liquid only holes. For solids activate the handle on the side to open the flapper to the compost bin. After you finish, close the flapper to seal the compost bin. Next turn the big crank handle a few times to mix the compost medium and the solids. An integral vent fan keeps the compost dry and helps to quicken the process.

Although boaters do feel a composting head is a bit of a learning curve, when set up and maintained its odor free. Plus you’ll never have to worry about clogged hoses, finding or paying for pump out stations again. There are almost no moving parts, almost nothing that could break, and next to no maintenance. You just need to clean it. The downside is you will have to come close to your waste during disposal but that’s not a bad trade off.

Where Does Toilet Waste Go On A Boat?

Dealing with toilet waste on a boat is much different from on land. As mentioned in the MSD section of this article, where waste goes depends on where the boat travels. Small vessels travelling close to shore tend to use the Porta-Potty or a composting head. Whereas a typical waste storage system for an offshore boat is a toilet plumbed to a holding tank. A holding tank system can range from simple and direct, up to complicated but versatile in use.

Below are explanations of how boats deal with and store toilet waste on a boat using holding tanks.


Porta-Potty & Composting Waste Systems

diagram of a Porta-Potty waste storage system for selecting a new boat toilet article

As mentioned in the type of marine toilets section, this is the solution for small boats. Owners of “weekender” boats need a way to hold small amounts of waste but don’t have space for a permanent head. Thus, many opt for the Porta-Potty waste option because it can hold around six gallons. In a cassette toilet the waste gets stored in two mini tanks under the head.

Boaters like that its easy to use and doesn’t clog. What stinks about this setup though is how close you come to your waste. As you have to take is on shore to dump it when it’s full.


Direct Discharge Waste System

diagram of a direct discharge waste system for a boat toilet

A direct discharge waste system is only for vessels that travel far offshore. In this marine system after waste exits the head unit it flows through a hose and out into the water. If you plan to travel in waters under 3-miles (4.83 km) offshore this isn’t the system for you. Not only is dumping raw sewage in our waters gross, inside the 3-mile limit is illegal too.

Dumping out waste inshore near beaches is harmful to many people. Including swimmers, divers and people who enjoy eating local fish/shellfish.

Another consideration is if you’re boating in foreign countries (e.g. the Caribbean). Many of these parts of the world don’t have waste pump out facilities. So, it’s best to discharge your waste overboard while underway in deep waters.

Seacocks and Thru–hulls

In most head systems, you need both a freshwater intake and black water output. To let the passage of fluids you need to drill holes through the hull with special fittings to stop sinking. A thru-hull is the fitting that accepts hoses and fittings to allow fluids in and out of the hull. A seacock is an attachment to the thru-hull to provide shut-off protection to the hose attached to it.

Most boats use a 3/4″ intake seacock and thru-hull for seawater flushing. For overboard discharge they use a 1 1/2 to 2″ seacock and thru-hull. Bronze seacock fittings are the most traditional due to their strength and durability. For metal hulls boats use Marelon fittings for their non-conductive, non-corroding nature.

Hose For Marine Plumbing Systems

Hose it is typical material used to transport fluids in hull plumbing systems. Keep in mind, sanitation hoses of any material will stink overtime if sewage sits inside them. While corrugated hoses and plumbing traps are cheap they will restrict waste flow. Whereas smooth walled hose or pipe promotes easy flow of fluids. If you have the space, try using a rigid hose/pipe material like PVC for long horizontal/sloped runs. This material traps odors and is great for flow.


Holding Tank Waste System Without Direct Discharge

diagram of a marine waste holding tank without a direct discharge output

Adding a holding tank allows boaters to travel under 3-miles from shore and use their marine head. The holding tank stores the waste inside the hull until you get to the marina or pump-out facility.

It uses the same freshwater seacock to the head unit but pushes waste to the tank. From the tank a macerating valve and pump-out hose finish the system. The best material for a holding tank is polyethylene (PE). This is because it’s lightweight, clean, non-permeable and won’t stink. Don’t use metal, most novices forget about the potency of urine as a corrosive liquid.

Waste Macerating Valve

A macerating valve in a marine waste system is like a garbage disposal for solid waste. The macerating valve turns on when you need to pump-out and empty the holding tank. If it doesn’t operate as expected, pumping out is difficult. Ensure to test this part of your system before hitting the water to ensure its working.


Holding Tank Waste System With Direct Discharge Option

diagram showing holding tank waste sytem with an added direct discharge option before the holding tank

This waste storage set up is the most versatile if you have the space in your boats’ hull. A common installation for this system is to place a “y-valve” between the toilet and the holding tank. Another is to install it after the holding tank. Using this system provides you with two discharge options. Either to direct waste overboard when you are beyond the three–mile limit. Or, if you are inshore, use the holding tank and pump out at the marina.


Marine Waste Y-Valve

A y-valve, also called a waste diverter valve, controls the flow of onboard waste. It diverts waste after the marine head into an onboard holding tank or overboard where it’s legal to do so. There are two installation options:

Upstream of holding tank:

Waste gets direct discharged in sea or sent to the holding tank. Any waste sent to the holding tank gets removed via a single pump-out hose.

  • Caveats:

Accidental discharge if valve is faulty. Some locales authorities don’t approve putting a y-valve upstream of a holding tank.

Downstream of holding tank

diagram of a marine waste y-valve installed after the holding tank

The waste get pushed through a single hose to holding tank. Next it moves into the y-valve which dumps into a hose to the water or an upward hose for pump-out. This makes local authorities happy and prevents accidental discharges.

  • Downsides Are Clogs:

The caveat with this setup is if the hose between the head and tank clogs. Clogs make doing maintenance a horrific experience.

User Tips For Marine Toilets


  • Prevent holding tank odors by ensuring the holding tank vent hose is clear. Or if you have the room increase the hose size of this vent to promote odorless aerobic bacteria in the tank. If you can’t increase the vent size on can’t vent at all, try a tank treatment to reduce odors.
  • Add vented loops into hoses of you waste system. Boats often sink due to dangerous backflow siphoning in marine heads. To prevent siphoning, install a vent loop above the waterline against the bulkhead.
  • Only use biodegradable toilet paper!
  • Use it in moderation: If it is yellow, let it mellow, if it is brown, flush it down.
  • Follow marine laws: The fines for overboard discharge of untreated sewage are rising. Get acquainted with the local pump-out facilities and personnel. One part bleach to 10 parts water should kill any bacteria in any cleanup.
  • Before you haul out the boat for storage. Flush, clean, and pump dry your holding tank. Out of the water, drain any water inside the toilet to prevent freeze-up damage during winter storage.

Finishing Up: Selecting A New Marine Toilet

Now you have the information to select a new marine toilet. Installing a new marine head is within the skill-set of a do-it-yourselfer. Although, if you’re a novice or upgrading from a manual head to a vacuum type. It’s in your best interests to consult with an experienced marine plumber.

Thank you for trusting us at Outdoors Informed to aid in your research. We like to help so you spend less time indoors and more time doing your business out on the water.

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