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How Do Cruise Ships Get Their Water


Modified: December 28, 2023

by Melonie Winchell



When you embark on a cruise ship adventure, you may find yourself marvelling at the luxury and amenities onboard. From gourmet dining to world-class entertainment, everything seems seamlessly provided for your comfort and enjoyment. But have you ever wondered about one essential resource that is required for the smooth sailing of these massive vessels? That’s right – water! Cruise ships rely on a sophisticated water supply system to ensure that their passengers and crew have access to safe and clean water throughout their journey.


In this article, we will explore how cruise ships obtain and manage water during their voyages. We will delve into the desalination processes they employ, the storage and treatment of water onboard, the onshore sources they tap into, and the environmental considerations that come into play.


Embarking on a cruise ship is like entering a self-contained floating city. These colossal vessels, carrying thousands of passengers, need to have a reliable and efficient system in place to provide water for drinking, cooking, cleaning, and other essential activities. Let’s dive into the fascinating world of cruise ship water supply!


Desalination Processes on Cruise Ships

Cruise ships are designed to operate in the open sea, where access to fresh water sources may be limited. To overcome this challenge, most cruise ships employ desalination processes to convert saltwater into freshwater suitable for various onboard uses.


The most common desalination method used on cruise ships is reverse osmosis. This process involves passing saltwater through a series of membrane filters at high pressure. The filters have tiny pores that block the salt molecules while allowing water molecules to pass through, producing fresh water. Reverse osmosis is highly efficient and can remove up to 99% of the salt content in seawater.


In addition to reverse osmosis, cruise ships may also utilize evaporators and distillers for desalination. Evaporators heat the saltwater to generate steam, which is then condensed to produce freshwater. Distillers work similarly by heating the water and collecting the condensed vapor as freshwater. These methods are effective but are less commonly used due to their higher energy consumption compared to reverse osmosis.


Desalination processes on cruise ships are sophisticated and require regular maintenance and monitoring to ensure optimal performance. The equipment used undergoes rigorous testing and maintenance to ensure the highest quality of freshwater is produced for the comfort and safety of the passengers and crew.


Reverse Osmosis Desalination

Reverse osmosis is the most prevalent method of desalination used on cruise ships. This process involves the use of membrane technology to remove salt and impurities from seawater, resulting in fresh and drinkable water.


The reverse osmosis desalination process starts by drawing seawater into the ship’s intake system. The water is then pre-treated to remove larger particles, such as debris and sediment, through filtration. After pre-treatment, the seawater is directed to high-pressure pumps that force it through a series of semi-permeable membranes.


These membranes consist of thin sheets with microscopic pores that are smaller than the salt molecules present in the seawater. When the seawater is pushed through the membranes under high pressure, the salt and impurities are left behind, while the fresh water molecules pass through the membranes and are collected for use on the ship.


Reverse osmosis is extremely effective at removing salt, minerals, and other contaminants, resulting in high-quality fresh water. However, the process is energy-intensive and requires significant pressure to force the seawater through the membranes, which can contribute to the overall energy consumption of the ship.


To optimize the reverse osmosis desalination process, cruise ships employ advanced technology to monitor and control the system. Sensors and automated controls continuously measure and adjust factors such as pressure, temperature, and flow rates to ensure optimal performance and water quality.


The fresh water produced through reverse osmosis is stored in dedicated tanks onboard the ship. It goes through further treatment, such as disinfection and pH adjustment, before being distributed for various uses, including drinking, cooking, showers, and laundry.


Evaporators and Distillers

While reverse osmosis is the most common method of desalination on cruise ships, evaporators and distillers are also utilized to produce freshwater.


Evaporators work by heating seawater to create steam. The steam is then condensed back into liquid form, leaving behind the salt and impurities. The condensed freshwater is collected and stored for use onboard the ship. Evaporators can be either single-effect or multiple-effect, depending on the number of stages involved in the evaporation process.


Distillers operate similarly to evaporators. They heat the seawater to produce steam, but instead of condensing the steam directly, it is passed through a separate condensing system. The condenser cools the steam, causing it to transform back into liquid form and separate from the salt and impurities. The resulting freshwater is collected for use onboard.


Compared to reverse osmosis, evaporators and distillers have higher energy requirements due to the need for heating the water. However, they are effective in removing salt and producing freshwater. These methods are commonly used as a backup or supplementary desalination system on cruise ships.


Evaporators and distillers also require regular maintenance to prevent scaling and fouling caused by the build-up of minerals and impurities. Cleaning procedures and inspections are performed regularly to ensure efficient operation and to maintain the quality of the freshwater produced.


It is worth noting that modern cruise ships often incorporate a combination of reverse osmosis, evaporators, and distillers to ensure a reliable supply of freshwater, even in challenging conditions. This diverse approach allows for flexibility and redundancy in the water desalination process, ensuring a consistent supply of freshwater for the passengers and crew.


Water Storage and Treatment

Once the seawater has been successfully desalinated through reverse osmosis, evaporators, or distillers, it is necessary to store and treat the freshwater onboard the cruise ship. This ensures that the water remains safe and suitable for various uses.


Cruise ships have dedicated storage tanks specifically designed to hold the freshwater produced through the desalination process. These tanks are constructed using materials that are safe for storing potable water and are regularly inspected to maintain their integrity and cleanliness.


Water treatment onboard a cruise ship involves several stages to ensure the highest quality. Chlorine or other disinfectants are added to the freshwater tanks to kill any remaining bacteria or microorganisms. Additionally, filtration systems may be employed to remove any particulates or impurities that may have passed through the initial desalination process.


In some cases, onboard water treatment may also involve adjusting the pH levels of the freshwater to ensure it meets the optimal range for consumption and use. This is typically done using chemicals to maintain a balanced and safe pH level.


Regular testing and monitoring are conducted to ensure that the treated freshwater remains within acceptable quality standards. Cruise ships adhere to strict regulations and guidelines for maintaining water quality, often following international standards set by organizations such as the World Health Organization (WHO) and the International Maritime Organization (IMO).


It is important to note that despite the rigorous water storage and treatment processes, cruise ship passengers should always follow any recommended precautions or guidelines provided by the ship’s staff. This includes being mindful of the importance of water conservation and the responsible use of freshwater during your cruise experience.


Onshore Sources and Resupply

While cruise ships have advanced desalination systems onboard, they also rely on onshore sources for water resupply during their voyages. These onshore sources can include ports, coastal facilities, or even specialized water supply vessels.


When a cruise ship docks at a port, it has the opportunity to replenish its freshwater reserves. Many ports have infrastructure in place to provide fresh water to visiting ships through water supply lines. Ships can connect to these lines and replenish their onboard freshwater tanks directly from the port’s supply.


In some cases, cruise ships may also send out water supply vessels, often referred to as “bunkering” vessels, to meet them at specific locations during their voyage. These vessels are equipped with large supplies of fresh water to transfer to the cruise ship’s storage tanks. This allows the ship to restock its freshwater reserves without having to dock at a port.


The frequency of onshore resupply depends on the ship’s itinerary and the length of the voyage. Cruise lines carefully plan their routes and schedule port visits strategically to ensure a sufficient supply of freshwater throughout the journey. Additionally, onboard water consumption is closely monitored to optimize water use and minimize the need for frequent resupply.


Regardless of whether the freshwater is sourced from a port or a water supply vessel, it undergoes a series of tests and treatment procedures to ensure its quality. This includes bacteriological and chemical testing to meet the necessary health and safety standards.


It is important to note that cruise lines are committed to sustainable practices, including responsible water management. They aim to minimize their environmental impact by implementing water conservation methods and utilizing technologies that optimize water usage and reduce wastage.


By leveraging onshore sources and resupply options, cruise ships can maintain a consistent supply of freshwater throughout their voyages, ensuring the comfort and well-being of their passengers and crew.


Environmental Considerations

While cruise ships rely on various methods to obtain and manage water onboard, it is crucial to address the environmental considerations associated with these processes.


One of the primary concerns is the impact of desalination on marine ecosystems. The intake of large amounts of seawater during the desalination process can inadvertently trap marine organisms and larvae, causing harm to marine life. To mitigate this, cruise ships employ advanced filtration systems to minimize the intake of marine organisms and implement policies to minimize the ecological impact.


The energy consumption required for desalination processes, especially through reverse osmosis, is another environmental consideration. Cruise ships are actively exploring and implementing energy-efficient technologies to reduce their carbon footprint. This includes the use of renewable energy sources, waste heat recovery systems, and more energy-efficient desalination systems.


Additionally, proper management of wastewater from these desalination processes is essential. Cruise ships must treat and dispose of the brine or concentrate, the byproduct of desalination, in an environmentally responsible manner. This may involve dilution and dispersion in open oceans or utilizing specialized brine discharge systems designed to minimize the impact on marine ecosystems.


Water conservation also plays a vital role in addressing the environmental impact of water usage on cruise ships. Cruise lines implement measures to promote water-saving practices among passengers and crew, such as encouraging shorter showers, providing information on water conservation, and utilizing water-saving technologies in onboard facilities.


Furthermore, cruise lines are increasingly investing in research and development to explore innovative technologies and sustainable practices in water management. This includes advancements in desalination processes, water recycling and reuse systems, and the use of alternative water sources such as rainwater harvesting and advanced purification techniques.


By incorporating these environmental considerations into their operations, cruise lines are committed to minimizing their ecological footprint and promoting sustainable water management practices. Efforts are continuously being made to strike a balance between providing passengers with a comfortable and enjoyable experience while ensuring the preservation of our precious marine ecosystems.



The water supply system on cruise ships is a complex and vital component of their operations. Through sophisticated desalination processes such as reverse osmosis, evaporators, and distillers, cruise ships are able to convert seawater into fresh and potable water for passengers and crew.


The freshwater produced goes through careful storage and treatment processes to ensure its cleanliness and safety. Cruise ships also rely on onshore sources and resupply options to maintain a sufficient supply of water during their voyages.


However, it is important to consider the environmental impact of these water management practices. Cruise lines are actively implementing measures to reduce energy consumption, minimize the intake of marine organisms, properly manage wastewater, promote water conservation, and explore innovative and sustainable technologies.


By addressing these environmental considerations, cruise lines aim to balance the needs of providing a comfortable onboard experience with the preservation of marine ecosystems. They continue to invest in research and development to achieve more efficient and eco-friendly water management solutions.


As you embark on your next cruise adventure, take a moment to appreciate the intricate water supply system that ensures your comfort and safety onboard. Be mindful of water conservation practices and support the cruise industry’s commitment to environmentally responsible water management.


By working together, we can all contribute to a sustainable future for the cruise industry and the preservation of our oceans and marine life.