How Does Plumbing Work on a Cruise Ship

When you’re on vacation you might not be thinking about where the water goes once you flush the toilet or rinse something down the drain. However you’re in the middle of the ocean and there isn’t a sewage system to hook up to when sailing along, so where does it go and how does it work? Well, here’s an explanation as to what happens to sewage on a cruise ship.

The Fresh Water Basics

Cruise ships use salt water for the water consumed by guests, however it isn’t just sea water out of the ocean. Previously, cruises would just use salt water but this lead to premature corrosion of the pipes. Currently ships will use desalination equipment: water is pulled from the ocean, run through the process and then transported to holding tanks. Some ships hold up to 2 million litres of fresh water at any time.

The desalination process will remove impurities and harmful minerals from the water, but adds in the important minerals found in drinking water. The water stored in these tanks will then be available for transportation to guest rooms, kitchens and where ever else it is needed on the ship.

The Sewage Basics

On every cruise ship there are two kinds of sewage: gray water and black water. Each one is whisked away from rooms into tanks called Gray Water Tank and Black Water Tank. Gray water is waste that goes down the drain (either a sink or a shower) and black water is waste that flushes down a toilet.

These tanks are typically stored away from the eyes of guests, but due to the number of people on a cruise ship they usually fill up quickly. When it’s time the water will be treated (as per regulations) and then will be dumped into the ocean while the ship is sailing.

There are specific regulations for dumping sewage, especially if the ship is within a certain distance from port but when the ship is out at sea the regulations are much more relaxed and it’s up to the cruise line to regulate.


Just like in your home, backups happen. On a cruise though, it’s a much bigger deal. People are stuck in small, confined spaces and being without running water is a big deal. Blockages in the pipes on a cruise ship are a huge deal: people are paying to be on vacation and a backup causing no running water will always be memorable. Cruises will have a plumber on board to make sure everything is running smoothly.

Plumbing on a cruise ship can be a logistical nightmare because, should there be a problem, people are stuck without water on a vacation they potentially paid a lot for and they are on a ship in the middle of an ocean. Fixing a plumbing problem on a cruise is important, and it’s critical it is done quickly. Modern day cruise lines employ a fantastic system for bringing in and removing water and waste, with leading edge environmental engineering technologies.

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