How Does a Marine Toilet Work? – Know In-Depth Information

How Does a Marine Toilet Work? – Know In-Depth Information

“Are there toilets on board?” – This is one of the most frequent questions that folks ask before they take part in a sailing adventure.

Yes, normally, there will be toilets, which sailors refer to as “heads” but these are somewhat different from what you have at home.

In this article, we’re going to find out how marine toilets work and learn your best options with these toilets.

So, why call them heads?

Does it sound strange to call them heads? Well, the term actually makes total sense, and here’s how:

Initially, in the good old days, only captains had private toilets at the ship’s back (these were situated near their quarters).

There was a toilet at the front part of the ship, and the rest of the crew had to make do with it (this one was near the waterline).

A toilet at the front part of the ship had its waste naturally washed out by the seawater, and since the ships traveled downwind (where the wind blows), unpleasant odors would be blown out speedily.

As you might guess, the front of the ship is also called the head, and that’s where the term “heads” referring to toilets comes from.

These days, heads are situated in almost any location on the ship, as ships are now designed with holding tanks as well as powered and manual pumps.

There’s no longer a need to use waves for washing out the waste into the water.

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How does a marine toilet work?

The work of a head is maintaining sanitation on the open sea. But there’s one major distinction between a normal toilet and a head that you got to note – the bowl that usually holds water in a normal toilet doesn’t ordinarily hold water in a marine toilet. Reason being?

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The water would spill easily in case of rough weather. Thus, the bowl is kept dry, and water is only pumped into it when one is ready to use the toilet.

Depending on the ship, there may be either a hand or power pump.

Before using the toilet, you have to flip the switch to pump water into the bowl, and as soon you’re done answering nature’s call, you flip the switch in the other direction, and the water, along with the waste, is pumped out. It’s that easy!

Caution: Don’t put anything else into the toilet apart from your body’s waste material and toilet paper. 

There are normally bins in the ship where you can put dental floss, hygiene products, and other waste items.

Environmental laws

These can differ across the globe, but in many nations, marine sanitation law forbids discharging raw sewage into the water near sensitive areas like islands and the mainland.

What are your marine toilet options?

Traditionally, ships flush the waste from their toilets either into the sea or into holding tanks that are then emptied onshore.

But, today, there are cheaper, more convenient options.

The law stipulates there shouldn’t be a discharge of untreated waste within one nautical mile of islands, the mainland or any reef. If your ship doesn’t have onboard sewage treading systems, options include:

  • Having portable toilets onboard and later emptying them into septic.
  • Retaining the waste in a holding tank until it can be pumped into an onshore facility.

Portable toilet

A portable marine toilet is a great option for a trailer boat. It’s linked up to a tank containing fresh water and another tank at the bottom where the waste is emptied.

The waste tank is removable so its contents can be emptied into a sewage collection area or a domestic toilet.


  • Lightweight
  • Inexpensive
  • Easy to install 
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  • Chemicals are required
  • There have to be at least 10 to 20 liters of water 

Composting toilets

Many ships are using composting toilets these days, as they don’t use chemicals or pollute the environment and they don’t smell. Composting toilets, which work by letting air dry and compost the waste, have 2 vessels – one for solids and another for urine.

 Sawdust or peat moss normally have to be added to the waste to boost the drying process.


  • Needs minimal maintenance
  • Long-lasting – up to a whole month for 2 people
  • No need to use water – this reduces the weight as well as the fuel consumption
  • Environmental friendly, as there’s no need to use chemicals
  • You don’t have to stress about blocked pipes
  • There’s no special disposal process; you just transfer it into the garden


  • The toilet is normally quite tall, and so it takes some getting used to

Cassette toilets

These have a built-in seat and a base that is removable. The base is where the waste is stored.


  • Inexpensive
  • Easy to use
  • Simply emptying 


  • The toilet can be very heavy
  • There can be odors
  • The rinsing water tank has to be kept refilled 

Parts of The Marine Toilet

Apart from the toilet itself, the other main parts include the pump and the storage/evacuation.

1. The Pump – How Does a Marine Toilet Work

A marine toilet pump is typically either hand-powered or electrical, but the function is similar.

There are 4 pipes on the system, which represent 2 systems – the wet system and the dry system. The 2 systems are switched between manually.

2. The Wet System

This is the system that pumps water into the tank. Seawater gets sucked into the ship via a valve located on the underside; the valve is known as the seacock. Before one uses the toilet, they pump water from the tank into the toilet bowl, and after using the toilet, they pump water again into the bowl for circulation of the contents, and then, the contents are flushed out.

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With every downstroke, clean water from the sea is sucked into the water tank.

3. The Dry System

This is the system that the user activates after using the toilet. When the water has circulated, and the bowl is clean, the dry system works to empty all the water in the bowl, to prevent spillage.

4. Storage/evacuation

There’s a one-way valve, known as the joker, where waste passes through from the toilet either into a storage tank or out into the sea.

How Does a Marine Toilet Work FAQ

1. What is a marine head?

A marine head is just another term for a marine toilet.

2. Where is marine toilet waste disposed?

The treated waste is normally stored in a small tank that’s incorporated in the toilet unit or transferred to a large sealed tank in the boat, after which it is disposed from the boat to an onshore disposal facility.

If you’re out in the sea and far away from dry land, you may dispose treated waste into the sea.

3. Can I dispose treated waste into inland waterways?

Usually, the overboard discharge of treated waste is permitted on inland waterways, but that may vary with state.

As for untreated waste, it is a rule of the thumb that you have to hold it in the boat’s storage till you transfer it to a disposal facility.

How Does a Marine Toilet Work Final Word

Whatever type of marine toilet you decide to use on your ship, don’t forget that water preservation is our duty as humans to mother nature.

Go for an environmentally friendly toilet and consider using phosphate-free biodegradable products.

Hope you have found our guide helpful. We have also prepared a guide on how does an anti siphon valve work. I hope you will also find it helpful too.

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