Cruise Ship Toilets: What Happens When You Flush? Step by Step Guide (2023)

If you’re considering a cruise you may be wondering what happens when you flush the toilet on a cruise ship.

I’ve been on a number of cruises to date and in this article, we will look at where sewage goes when you flush a cruise ship toilet.

What Happens When You Flush a Cruise Ship Toilet?

When a toilet is flushed on a cruise ship, the sewage travels to the onboard treatment plant. Here the waste is filtered before it enters an aeration chamber. The aeration chamber cleans the waste. It is then sterilized using UV light and released into the ocean when clean enough to do so.

Each person on a cruise uses 40-50 gallons of water per day. Reducing the amount of water used is a high priority for all cruise ships and as a result even the toilets are designed to save water.

1. The Guest Flushes The Toilet

The process starts when the guest flushes the toilet after using it.

Cruise ship toilets use a suction system, which is designed to reduce the amount of water needed in order to complete the flush.

It might not seem as though this is saving a lot of water, but if you were to multiply the saving by the number of guests and number of times they use the toilet per day, this saving can be HUGE.

How do Cruise Ship Toilets Work?

There is water in the bowl of the toilet prior to it being used but there is no extra water that flushes down the waste, instead, the waste is sucked down.

Suction toilets make perfect sense on cruise ships, as it reduces the amount of water needed considerably.

I remember cruising as a child and being terrified of the loud suction sound of the toilet. Some cruise ships also have automatic sensors that flush the toilet when the guest stands which was one of the reasons I was so afraid of the loud noise. It went off once when I was still sat down and it scared me so much!

(Video) What Happens After You Flush on a Cruise Ship

  • Cruise Ship Toilets: What Happens When You Flush? Step by Step Guide (1)

How do You Flush a Cruise Ship Toilet?

The flush button on a cruise ship toilet is usually located behind the lid as you can see in the photo above. This is so that the guest using the toilet has to put down the seat before they can flush the toilet.

Nothing awful will happen if you manage to flush the toilet with the seat still up. You’re not going to get sucked down the toilet, but the idea is to only flush it when the toilet lid is down.

On some older ships, you may find that there is a delay between pressing the button and the flush operating.

I took a cruise on a cruise ship from the 1980s and you could press the flush button, wash your hands and leave the bathroom before it actually flushed. Not a problem, just confusing at first!

NOTE: It’s important to remember that cruise ship toilets cannot handle things like tampons or wipes. These will block the cruise ship toilet and as the toilets are all linked together, if you block your toilet, it’s likely to affect other cabins.

The following items cannot be put in cruise ship toilets:

  • Wipes
  • Paper towels (kitchen towels for example), toilet paper is fine!
  • Condoms (no idea why anybody would do this, but DON’T)
  • Tampons/Pads (This one can be a bit strange but tampons have to be wrapped up and placed in the bin as they can easily break the systems. Cruise lines provide sanitary bags for this purpose).
  • Cotton Swabs/Pads
  • Any Chemicals or Toiletries

Generally speaking, if it isn’t a natural material or tissue paper, don’t flush it down a cruise ship toilet.

2. The Sewage Enters The Treatment Plant

Cruise ships have sewage treatment plants onboard, where they treat the waste. The sewage that comes from the toilets is what is called black water.

  • Cruise Ship Toilets: What Happens When You Flush? Step by Step Guide (2)

Gray water doesn’t have to go through the same treatments as black water, although it is still filtered before being released.

Some gray water is mixed with the black water in order help the black water cleaning process.

(Video) How To Flush a Boat or Ship's Toilet "Head"

What is the difference between black water and gray water?

The difference between black water and gray water, is that it comes from a different place. Black water comes from toilets on board a ship and gray water comes from the onboard laundry, showers, and kitchens.

Common places for black water to come from include:

  • Toilets

Common places for gray water to come from include:

  • Laundry
  • Showers
  • Sinks
  • Kitchens

Gray water is ‘cleaner’ than black water and is unlikely to have anything nasty or dangerous lurking within it.

3. Waste is Filtered in The Sewage Treatment Facility

When the waste first enters the plant it goes though a filter.

This is a very basic filter which filters out any parts which wouldn’t be suitable to be sterilized and released.

The parts that don’t go through the filter are then stored and taken off onto land when the ship docks.

  • Cruise Ship Toilets: What Happens When You Flush? Step by Step Guide (3)

4. Waste Goes Into an Aeration Chamber

An aeration chamber is a tank where bacteria are used to biodegrade the waste matter. The bacteria need oxygen to function, so the chamber has air blown into it.

Wastewater aeration is the process of adding air into wastewater to allow aerobic bio-degradation of the pollutant components. It is an integral part of most biological wastewater treatment systems. Unlike chemical treatment which uses chemicals to react and stabilize contaminants in the wastewater stream, biological treatment uses microorganisms that occur naturally in wastewater to degrade wastewater contaminants.


The microbes within the water feed on the waste and this is basically a fast-forwarded form of decomposition. The cruise line has to be very careful that it doesn’t do anything to affect how these bacteria work, this is why only certain cleaning chemicals are used when cleaning onboard toilets.

(Video) Proper RV Toilet Operation | Teach Me RV!

  • Cruise Ship Toilets: What Happens When You Flush? Step by Step Guide (4)

5. Waste Enters a Settlement Chamber

In the settlement chamber, the waste is able to settle and separate. The thicker dirtier part sinks to the bottom as the water rises to the top.

The part that falls to the bottom is sent back to the start of the process to go through the aeration chamber again.

  • Cruise Ship Toilets: What Happens When You Flush? Step by Step Guide (5)

6. Water Sterilized

At this point, the water is usually sterilized by the cruise line. The most common way to do this is with UV light, although some lines do this differently.

Chlorine isn’t usually used as this could be a risk to marine life.

After being sterilized, the water is considered to be clean enough to dispose of. It is stored in tanks on the ship until the ship is ready to dispose of it.

There are tests that are carried out by the cruise line in order to make sure that the water is of a high enough standard to do this.

7. Water Released into The Ocean

At this point, the water is clean enough to be released into the ocean. It’s arguably a lot cleaner than a lot of the other water in the ocean!

There are many different regulations about how far a cruise ship has to be from land and at what speed they must be sailing for the sewage to be disposed of. A common distance is 12 nautical miles.

Many cruise lines go above and beyond the minimum requirements.

Was it Always Like This?

In the past, cruise lines used to be able to just release sewage directly into the sea whenever they wanted to.

(Video) How to clean public toilet in Cruiseship

This wasn’t such a big problem as there weren’t as many huge cruise ships as there are today. Regulations related to cruise ship waste is constantly evolving and being updated.

What About Laid up Ships?

The need to go to out to sea in order to release wastewater, is one of the main reasons that cruise ships when laid up in 2020 still had to sail and couldn’t turn off.

To find out more about what happens to ships in cold layup, check out the video below:

To conclude: When you flush a toilet on a cruise ship the wastewater goes to the treatment plant on board. It is cleaned and released when safe to do so.

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What happens when you flush toilet on cruise ship? ›

When a toilet is flushed on a cruise ship, the sewage travels to the onboard treatment plant. Here the waste is filtered before it enters an aeration chamber. The aeration chamber cleans the waste. It is then sterilized using UV light and released into the ocean when clean enough to do so.

What happens to toilet water on a ship? ›

Most ships add it to the black water and pass it for sewage treatment. Many companies simply discharge it into the sea.

Do cruise ships have flush toilets? ›

The toilet in your cruise ship bathroom will not be a standard water-flush system like you have at home. Water is a precious resource onboard a cruise ship, so modern ships save gallons with each flush by using a vacuum system.

Do cruise ships have jail? ›

If you wonder whether cruise ships have jails, the answer is yes. Jails are called brigs on a cruise ship and tend only to be used in serious circumstances when no other options are available. Cabin arrest is typically used before the brig is needed.

Does toilet water go into the ocean? ›

Chemicals are added to kill as many germs as possible. Then the treated water is released into a local river or even the ocean. If you live near the coast your treated sewage probably goes into the ocean. The treated sewage is cleaned to make sure that it does not cause environmental problems.

What are the 7 steps for cleaning toilets? ›

7 Tips for a Cleaner Toilet
  1. Clean it often. Bathrooms are filled with germs and should always be cleaned once a week - especially your toilet. ...
  2. Use vinegar to clean. ...
  3. Reach for a toothbrush. ...
  4. Get the right brush. ...
  5. Keep disinfecting wipes on the toilet. ...
  6. Don't ignore the handle. ...
  7. Avoid carpets.

What are the only 3 things you should flush down the toilet? ›

There are only three things you can safely flush down the toilet into the sewer system —pee, poo and (toilet) paper. Just remember those three as the three Ps that you can flush. And don't forget, "flushable" wipes are not really flushable.

What happens after US Navy sailors flush the toilet on an aircraft carrier? ›

“Most of the sewage waste produced on an aircraft carrier comes from the toilets' urinals,” the video continues. After entering an integrated treatment system, a complex array of filtration and cleaning methods are applied, including the use of a bio-reactor and a sediment tank for processing.

What is a toilet on a ship called? ›

Head (ship's toilet) The use of the term "head" to refer to a ship's toilet dates to at least as early as 1708, when Woodes Rogers (English privateer and Governor of the Bahamas) used the word in his book, A Cruising Voyage Around the World.

Why do ships don't sink in water? ›

A ship which has a large weight displace a large volume (thus large weight) of water. Hence the buoyancy force acting on the ship is much greater than the weight of the ship itself, making it to float on water. Thus ship do not sink in water.

Where do toilets flush on ships? ›

The main feature of a boat's toilet is that it flushes directly into the water. As it is below the boat's surface, there's a hole in the hull through which its contents have to be pumped out. This operation may be a little scary the first time, but it is not difficult at all.

How do cruise ships get water for showers? ›

Shipboard potable water (drinking, bathing, whirlpools, etc.) either comes from a shoreside water treatment plant or is generated on board from seawater via Reverse Osmosis systems or Evaporators.

Do cruise ships provide condoms? ›

Some cruise lines do understand that the salt sea air and ocean waves can lead to romantic encounters. Royal Caribbean and MSC passengers do have access to condoms, pregnancy kits and lubrication, while P&O, Cunard and Princess have the morning after pill.

Do cruise ships have rats? ›

While there has been a rising concern and increased prevention of rodent activity on cruise ships/large vessels, chances are there will always be a potential for this problem.

Do cruise ships carry guns? ›

All weapons are prohibited on cruises due to cruise ship security regulations. Guns are not allowed, with or without a concealed carry permit. Mace, pepper sprays and knives of any type are prohibited. The information contained on this website is provided as a service to USCCA, Inc.

Are there murders on cruise ships? ›

Although cruise ship murders are incredibly rare, they do happen.

Does shower water and toilet water go to the same place? ›

You see, every drain in your home is connected to a pipe that moves used water from your house to a sewer in the street; that's right, every toilet, shower, sink, washing machine, dishwasher, and anything else that uses water connects to one singular pipe.

Is toilet water clean after flushing? ›

Is The Water In The Toilet Dirty? The water in your toilet bowl is actually clean. Sure, it is full of bacteria, but that is because it contains sewage—which, by definition, is wastewater that contains human waste. However, the water itself is relatively clean and poses no health risk.

Do they dump sewage in the ocean? ›

First, ships are allowed to dump untreated sewage into the ocean as long as they are further than 12 nautical miles from the coast. Think about that. Raw sewage can be dumped into the vast majority of the ocean.

What are the 7 steps in the 7 step cleaning process? ›

7 Step Cleaning Process
  1. Knock on Door/ Place wet floor sign outside work area.
  2. Empty trash and clean waste receptacle inside and out. ...
  3. High dust – Work counterclockwise around the room. ...
  4. Damp wipe surfaces. ...
  5. Stock supplies – soap, paper towels, toilet tissue.

What is the first step in cleaning the toilet and bathroom? ›

First, clear the floor of all items, such as baskets, towels, toilet plungers, etc. Second, sweep up any dust that collected on the floor, especially in the corners. Third, use a vacuum to remove any remaining debris. Fourth, mix warm water and an all-purpose cleaner in a bucket, and mop the floor.

When cleaning a toilet the first step in the process is to? ›

1. Turn on all the lights & the exhaust fan. 2. Flush the toilet, apply product to bowl & allow to stand.

What are 2 things you should never flush down a toilet? ›

Cotton balls, cotton pads, and Q-Tips are definitely not safe to flush — they don't break down the way toilet paper does, and all they really do is clump together in your pipes and cause problems down the line.

What should you never flush down the toilet? ›

Any Type of Plastic

It doesn't matter if it's packaging plastic or a Band-Aid, you can't flush plastics down a toilet. Plastic doesn't dissolve and can cause many problems in your pipes—if they get that far after a toilet flush.

Where does poop and pee go when you flush? ›

The sewerage system pumps the sewage to a treatment plant where it is processed and treated to remove any contaminants. Once treated, the resulting effluent is released back out into waterways, where it continues its journey through the water cycle.

How much does it cost to flush a toilet on an aircraft carrier? ›

It costs the Navy $400K per flush to unclog its prized carrier's oft-congested plumbing. The Navy's prized new super carrier was meant to be a symbol of American military might over the world's oceans, but it is the ship's toilets and plumbing system that are proving to be obstacles the service has yet to master.

Why is toilet is head in ship? ›

Since the wind was blowing from the rear to the front, the “head” (or front) of the ship was the best place for sailors to relieve themselves. So, when the shipmates went to the toilet, they went to the head. (I guess a sailor could have said, “I'm going to the bow.”)

Why is a toilet called a John? ›

The name “John” was later derived from “Jake” and “Jack.” Secondly but most notable amongst historians, John was the name of the first man credited with inventing the first flushing toilet. John Harington was born during the time in which Queen Elizabeth reigned.

What is it called when you put someone's head in the toilet and flush? ›

A swirly or swirlie is a form of bullying in which the victim's head is put into a toilet. Some people have questioned whether swirlies are real or whether they were invented for television and other fiction.

What is a shower called on a ship? ›

Random Boat Facts, why a Boat bathroom is called a head -

Can you survive a ship sinking? ›

Fortunately, the odds of surviving a sinking ship are very high. The most important thing to do is stay calm.

How do cruise ships not tip over? ›

Essentially, a cruise ship stays upright because they keep all of the heaviest equipment below deck. This has the effect of keeping a low center of gravity. In addition, the shape of a cruise ship's hull is wide and rounded, which helps it move through the ocean smoothly and with minimal drag.

Why do ships float when their nails sink? ›

The weight of the water displaced by the ship is equal to its weight, so it floats. Whereas the weight of the water displaced by the iron nail is less than its weight so the iron nail sinks.

How does sea toilet work? ›

The pump-out toilet comes either as a 'Dump-Through' unit (where the tank sits directly beneath the toilet) or with a remote tank, where the waste has to be transported away by pumps or vacuums via a pipe network.

How do you use the toilet on a ship? ›

Depending on the vessel, you may have to use a hand pump to operate the head. Once you've done your business, you'll need to flip a switch which allows you to pump water into the toilet bowl. Next, you flip the switch the other way, and you can pump the bowl out. Simple!

Can I drink tap water on cruise ship? ›

Cruise ship tap water is safe to drink unless you are told otherwise by the ship's authorities. The water throughout the ship has been treated, filtered and frequently tested to meet the standards of the World Health Organization and the U.S. Public Health Service on ships sailing into and out of U.S. ports of call.

Why do cruise ships drain the pools at night? ›

Cruise lines drain their swimming pools at night to discourage guests from trying to enter the pool when it is closed. Draining the swimming pools each night also allows the cruise lines to replace the water with clean water and a drained swimming pool is safer if the weather is rough.

What happens when you flush the toilet on a cruise ship? ›

When a toilet is flushed on a cruise ship, the sewage travels to the onboard treatment plant. Here the waste is filtered before it enters an aeration chamber. The aeration chamber cleans the waste. It is then sterilized using UV light and released into the ocean when clean enough to do so.

What is forbidden items on the cruise line? ›

Prohibited items:
  • Firearms & Ammunition, including realistic replicas.
  • Sharp Objects, including all knives and scissors. ...
  • Illegal Drugs & Substances.
  • CBD Oil / CBD Products.
  • Candles, Incense, Coffee Makers, Clothes Irons, Travel Steamers & Hot Plates. ...
  • Hoverboards.

Can you wear jeans on a cruise ship? ›

Acceptable attire includes sportswear, collared shirts, pants and jackets (if desired, but not required) for men and sportswear, casual dresses, or skirts and pants with blouses or knit tops for women. Regular, but not torn or distressed jeans, are fine.

Do hookups happen on cruises? ›

It shouldn't be a surprise, then, that hookups can and do happen on a cruise. Call it love, call it romance, call it a one-night stand. No matter what you call it, there are people on every cruise that end up getting down after meeting on the ship.

Can you flush tampons down the toilet on a cruise ship? ›

The only things that should go down a ship toilet is body 'stuff' and toilet paper. (If the toilet backs up it is a major problem and you could be charged for the back up.) Everything else is disposed of in the trash can. The room steward will provide bags or you can bring your own.

What do cruise ships do with sewage waste? ›

Hazardous waste generated onboard cruise ships are stored onboard until the wastes can be offloaded for recycling or disposal in accordance with RCRA.

Can you get condoms on a Carnival cruise? ›

6. Toiletries, Make-Up, Etc. While you shouldn't plan on buying these items on the ship as they are heavily marked up, know that you don't need to panic if you forget toothpaste. Bonus Perk: “Etc.” includes condoms (even on Azamara).

How many cruise ships sink a year? ›

Only four ocean cruise ships have sunk while on a cruise in the last 50 years. Assuming an average of 100 sailings per ship per year, and an average of 150 cruise ships in that time, that is odds of 1 in 187,500.

What happens if I accidentally flush a tampon? ›

Tampons do not immediately clog up your toilet after one flush so it may seem like they are safe to flush. Instead, flushed tampons build up over time. Once one gets stuck, it becomes easier for other tampons and non-flushables to get snagged and clog up the pipes.

Do cruise ships put laxatives in their food? ›

Apparently, there is a trend on cruise ships to put extra fat in the food which can have a laxative effect on a person. This is to make sure all of the ship's plumbing works properly and that there is little to no chance of the plumbing getting clogged or backed up.


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