Off the coast in the Gulf of Mexico, a worker enjoys a refreshing shower after working a long 12-hour shift. The water flows clearly and strongly, just as it should. However, this water represents a complicated system of filtration, disinfection, storage, and monitoring that ensures crew members have access to clean water they need for life and work at sea for weeks.
Potable water systems on offshore platforms and vessels are essential for daily life, yet they often go unnoticed. These systems transport thousands of gallons of water each day, maintaining quality amid unpredictable conditions. In confined spaces, the risk of contamination can spread quickly.
Failures in water filtration and transport systems can expose workers to dangerous waterborne diseases. Additionally, the tanks and systems can pose risks such as entrapment, toxic exposure, and asphyxiation. It's vital to understand these dangers and how they are managed to ensure the safety of maritime workers.
Two Paths to Potable Water: Bunkering & Desalination
Offshore platforms and vessels get their drinking water mainly through two methods: bunkering from shore supplies or producing it onboard through desalination.
Bunkering involves loading potable water from shore into the rig or vessel through special hoses and connections. Supply ships bring water from ports to offshore locations, where it is then loaded into onboard storage tanks. Hoses used for potable water must be dedicated solely for this purpose, must be capped when not in use, and must be disinfected if they have been idle for more than 14 days. Before bunkering starts, water samples must be tested.
Risks of contamination arise if hoses are not flushed correctly or if connections aren’t sealed properly. Water that meets quality standards on land might degrade during transport and storage if not managed well.
Desalination using reverse osmosis (RO) is a more sustainable method, allowing platforms and vessels to create their own freshwater from nearby seawater. The technology functions by pushing seawater through membranes under high pressure, allowing only water molecules to pass while blocking salts, minerals, bacteria, and viruses.
The desalination process starts with taking in seawater, often from about 20 to 30 feet deep to avoid contaminants on the surface. This raw seawater goes through pre-treatment to remove larger particles, sediment, and organic matter that could harm the membranes. After pre-treatment, high-pressure pumps move the water through the membranes. Fresh water comes out on one side, and concentrated brine is released back into the ocean.
Modern offshore RO systems can produce hundreds to tens of thousands of gallons of fresh water daily, depending on the size of the platform and the crew size. This method is energy-efficient compared to older thermal distillation methods, but it requires careful monitoring because performance and water quality can be affected by membrane fouling, mineral buildup, or biological growth.
How Distribution & Storage Works
Potable water must be stored and moved safely to reach crew quarters, galleys, and other points of usage. This is often where issues arise.
Potable water storage tanks on offshore structures can hold from a few thousand to tens of thousands of gallons. These tanks must be made from materials approved for drinking water, with coatings resistant to corrosion that won’t leach harmful substances. While steel tanks are common, they come with a challenge: rust. When steel oxidizes, it depletes oxygen in the water, creating conditions that foster bacterial growth, including Legionella.
Distribution piping carries water from storage tanks to taps, showers, and other fixtures throughout the platform or vessel. The piping material greatly affects water quality. Traditional steel pipes corrode over time, while newer systems use stainless steel, copper, or plastic to reduce these issues. However, older platforms might still use decades-old steel pipes that need constant maintenance.
Water temperature in the distribution system is crucial for preventing bacterial growth. The CDC advises that hot water should be stored above 140°F and cold water below 77°F, although Legionella can grow at temperatures as low as 68°F. If hot water systems don’t maintain high temperatures or if cold water isn’t kept cool enough, they create ideal conditions for bacteria to thrive.
Chlorination is the main defense against waterborne pathogens, with offshore sites typically maintaining chlorine levels of 0.2 to 0.5 milligrams per liter. However, keeping proper chlorine levels consistent throughout a complex distribution system, especially with infrequently used fixtures, requires diligent monitoring.
Legionella & Waterborne Illness
Legionella pneumophila is the most serious waterborne health threat to offshore and maritime workers. This bacterium causes Legionnaires' disease, a severe type of pneumonia that kills about 10% of those infected and poses significant risks for workers over 50, smokers, and those with weakened immune systems.
Legionella is naturally present in freshwater but becomes a risk when it multiplies in human-made water systems. When contaminated water becomes a fine spray (aerosolized) through showers, cooling towers, or other devices, workers can inhale droplets containing the bacteria and fall ill.
The risk on maritime vessels is high if drinking water systems are not properly maintained. A 2018 study found that 58% of water samples from 360 non-passenger merchant vessels docked at UK ports tested positive for Legionella, with 27% showing levels requiring immediate action.
According to the CDC, Legionnaires’ disease has an incubation period of 2 to 14 days, with symptoms like fever, cough, shortness of breath, muscle aches, and headaches. The disease doesn’t spread between people, but a single contaminated system can make multiple workers sick at once. For offshore workers, where medical evacuation can take time and onboard medical facilities are limited, an outbreak of Legionnaires’ disease can quickly become life-threatening.
In addition to Legionella, other waterborne pathogens pose threats. Coliform bacteria, such as E. coli, indicate fecal contamination and can cause gastroenteritis. While norovirus outbreaks on cruise ships make the news, similar gastrointestinal illnesses can also severely affect offshore crews, who live closely together and share common facilities. The major difference is that vessels and offshore installations may be far from shore, with limited medical resources to handle an outbreak.
U.S. Regulations & Oversight
The rules governing water quality for seamen and offshore workers involve multiple federal agencies and international standards.
The U.S. Coast Guard is primarily responsible for vessel sanitation and the quality of drinking water on ships within its authority. The Coast Guard enforces standards for water production, storage, and distribution on vessels and conducts inspections to ensure compliance with federal regulations.
The Maritime Labour Convention (MLC) 2006, effective since 2013, set international standards for potable water on ships. Regulation 3.2 mandates that vessels provide safe drinking water for crew use, food preparation, and personal hygiene. The convention requires that the water must be of a suitable quality and quantity, without causing harm to users.
For offshore installations in federal waters, oversight is less streamlined. While BSEE manages safety and environmental protection, potable water quality on fixed platforms often lacks clear federal supervision compared to vessels. Industry guidelines and companies’ safety management systems must address these gaps.
Maintaining Potable Water Standards: What Needs to Be Done
Potable water systems must be properly monitored and controlled to ensure safety for offshore crews and seamen who depend on them.
This entails:
• Regular Water Quality Testing & Transparency: Potable water should be tested regularly for Legionella, coliform bacteria, chemicals, and other contaminants. Monitoring must be proactive, not reactive, to maintain safe and consistent water quality.
• System Design & Maintenance: Older installations with aging steel pipes and tanks need upgrades using materials that resist corrosion and bacterial growth. Dead-end sections and rarely used taps or showers require regular flushing. Water temperatures should be kept at safe levels to discourage bacterial growth.
• Training & Education: All workers should be trained on the risks of waterborne illnesses, hygiene practices, and how to report water quality issues.
• Water Safety Plans: Every offshore installation and vessel should maintain a thorough, regularly updated Water Safety Plan that identifies potential contamination points, sets up monitoring procedures, and outlines clear protocols for addressing water quality problems.
The technology is available to provide safe, high-quality drinking water for offshore workers. Reverse osmosis systems can efficiently produce freshwater from seawater. Modern materials can prevent corrosion and bacterial growth, and monitoring equipment can detect contamination before health issues arise. What’s often lacking is the dedication to implement and maintain these systems properly.
For offshore workers, having access to potable water is not just a convenience or luxury; it is essential for their health, safety, and ability to perform in a demanding and challenging environment.
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