How Potable Water Quality Impacts Crew Health & Safety

Dozens of miles offshore in the Gulf of Mexico, a worker turns on a shower after a 12-hour shift. The water flows clear and strong, unremarkable in every way, just as it should be. However, that water represents a complex network of filtration, disinfection, storage, and monitoring that provides crew members with the clean water they need to live and work at sea for weeks at a time.  

Potable water systems on offshore platforms and maritime vessels are critical infrastructure that crews rely on every single day, yet they operate largely out of sight and out of mind. These systems must transport thousands of gallons of water daily, maintain quality through unpredictable conditions, and do so in an environment where contamination can spread rapidly through confined quarters. 

When water filtration and transportation systems fail, they place workers at risk of contracting deadly waterborne illnesses. Water tanks and systems themselves may also present hazards related to entrapment, toxic exposure, and asphyxiation. Understanding these dangers and the measures in place to prevent them is critical to maritime worker safety.

Two Paths to Potable Water: Bunkering & Desalination

Offshore platforms and vessels obtain potable water through two primary methods: bunkering from shore-based supplies or producing it onboard through desalination. 

Bunkering involves loading potable water from land-based sources onto the rig or vessel through specialized hoses and connections. Supply vessels transport water from port facilities to offshore installations, where it’s transferred into onboard storage tanks. Hoses used for potable water must be dedicated solely for that purpose, properly capped when not in use, and disinfected if they’ve been idle for more than 14 days. Water samples must be taken and tested before bunkering begins. 

Contamination risks are present when hoses are not flushed properly or when connections are not sealed correctly. Water that passed quality standards on shore might deteriorate during transport and storage if not appropriately managed.

Desalination through reverse osmosis (RO) offers a more sustainable alternative by allowing platforms and vessels to produce their own freshwater from seawater, which is abundant all around them. The technology works by forcing seawater through membranes under high pressure. The membranes allow water molecules to pass through while blocking dissolved salts, minerals, bacteria, and viruses.

The desalination process begins with seawater intake, often drawn from about 20 to 30 feet below the surface to avoid surface contaminants. Raw seawater passes through pre-treatment systems to remove larger particles, sediment, and organic matter that could damage the delicate membranes. High-pressure pumps then force the pre-treated water through the membranes. Fresh water emerges on one side; concentrated brine is discharged back to the sea on the other.

Modern offshore RO systems can produce anywhere from a few hundred to tens of thousands of gallons of fresh water every day, depending on the size of the installation and crew. The technology is efficient, consuming far less energy than older thermal distillation methods, but the systems are complex and must be monitored. Performance and water quality can all be affected by membrane fouling, mineral buildup, or biological growth. 

How Distribution & Storage Works

Potable water must be stored and distributed safely to reach crew quarters, galleys, and other points of use. This is where many problems begin.

Potable water storage tanks on offshore installations and vessels may range from a few thousand to tens of thousands of gallons in capacity. These tanks must be constructed from materials approved for potable water use, with coatings that resist corrosion and don’t leach contaminants. Steel tanks are common, but they present a significant challenge: rust. As steel oxidizes, it consumes oxygen from the water and creates conditions favorable for bacterial growth, including Legionella. 

Distribution piping carries water from storage tanks to taps, showers, and other fixtures throughout the installation or vessel. The type of piping material makes a considerable difference in water quality. Traditional steel piping corrodes over time. Newer systems use stainless steel, copper, or plastic piping to minimize these issues, but older platforms often retain decades-old steel pipe that requires constant attention and maintenance.

Water temperature within the distribution system is another key factor in preventing the growth of bacteria. The CDC recommends storing hot water at temperatures above 140°F and storing and circulating cold water at temperatures below 77°F, although Legionella can grow at temperatures as low as 68°F. Hot water systems that don’t maintain sufficiently high temperatures and cold water systems that aren’t kept adequately cool both create ideal conditions for bacterial growth.

Disinfection through chlorination is the primary defense against waterborne pathogens, and offshore installations typically maintain a chlorine level of 0.2 to 0.5 milligrams per liter. But maintaining proper chlorine levels throughout a complex distribution system, especially one with dead legs or infrequently used fixtures, requires careful monitoring. 

Legionella & Waterborne Illness

Legionella pneumophila represents the most significant waterborne health threat to offshore and maritime workers. This organism causes Legionnaires’ disease, a severe form of pneumonia that kills approximately 10% of those infected and can be particularly dangerous for workers over 50, smokers, or those with compromised immune systems.

Legionella occurs naturally in freshwater environments but becomes a health hazard when it multiplies in man-made water systems. When contaminated water is aerosolized (turned into a fine spray or mist) through showers, cooling towers, or other spray-producing devices, workers can inhale the bacteria-laden droplets and become infected.

The risk on maritime vessels is substantial when potable water systems are not properly monitored and maintained. A 2018 study examining water samples from 360 non-passenger merchant vessels docked at UK ports found that 58% tested positive for Legionella, with 27% of samples showing levels above the upper action limit (when immediate remediation is required). 

According to the CDC, Legionnaires’ disease has an incubation period of 2 to 14 days. Symptoms include fever, cough, shortness of breath, muscle aches, and headaches. The disease doesn’t spread from person to person, but a single contaminated water system can simultaneously sicken multiple workers. For offshore and maritime workers, where medical evacuation may take time and onboard medical facilities are limited, a Legionnaires’ outbreak can quickly become life-threatening.

Beyond Legionella, other waterborne pathogens pose risks. Coliform bacteria, like E. coli, indicate fecal contamination and can cause gastroenteritis. While cruise ship norovirus outbreaks make headlines, similar gastrointestinal illnesses can devastate offshore crews, where workers live in close quarters and share common facilities. The difference is that vessels and offshore installations may be miles from shore, with limited medical facilities and personnel on board to manage an outbreak.

U.S. Regulations & Oversight

The framework governing potable water quality for seamen and offshore workers involves multiple federal agencies and international standards.

The U.S. Coast Guard has primary responsibility for vessel sanitation and potable water quality on ships under its jurisdiction. The Coast Guard enforces standards for water production, storage, and distribution systems aboard vessels and conducts inspections to verify compliance with federal sanitation requirements.

The Maritime Labour Convention (MLC) 2006, which entered into force in 2013, established international standards for potable water on ships. Regulation 3.2 requires that vessels provide adequate supplies of safe drinking water for crew consumption, food preparation, and personal hygiene. The convention mandates that water must be of appropriate quality and quantity, and itmust not cause immediate or long-term harm to those using it.

For offshore installations in federal waters, oversight is less centralized. While BSEE regulates offshore safety and environmental protection, potable water quality on fixed platforms falls into a regulatory gray area with less clear federal oversight compared to vessels. Industry guidelines and company safety management systems must fill this gap.

Upholding Potable Water Standards: What Needs to Be Done

Potable water systems must be correctly (and continually) monitored and controlled to ensure the safety of the offshore crews and seamen who rely on them.  

This includes:

• Mandatory Water Quality Testing & Transparency: Potable water should be tested regularly for the presence of Legionella, coliform bacteria, chemicals, and other contaminants. Testing cannot wait until problems are already evident. Proactive monitoring keeps water quality safe and consistent. 

• System Design & Maintenance: Older installations with aging steel piping and storage tanks should be systematically upgraded with materials that resist corrosion and bacterial colonization. Dead-end sections and infrequently used taps or showers must be flushed regularly. Water temperatures must be kept at safe levels to inhibit bacterial growth.

• Training & Education: All workers should receive training on waterborne illness risks, proper hygiene practices, and how to report water quality concerns. 

• Water Safety Plans: Every offshore installation and vessel should have a comprehensive, regularly updated Water Safety Plan that identifies all potential contamination points, establishes monitoring procedures, and defines clear protocols for responding to water quality issues. 

The technology exists to provide safe, high-quality potable water to offshore workers. Reverse osmosis systems can produce fresh water from seawater with efficiency and reliability. Modern materials resist corrosion and bacterial growth. Monitoring equipment can detect contamination before it causes illness. What’s often missing is the commitment to implement these systems properly and maintain them rigorously over time.

For offshore workers, potable water isn’t just a convenience or a luxury. It’s a necessity that directly impacts their health, safety, and ability to perform demanding work in an already challenging environment. 

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Arnold & Itkin has been fighting for injured maritime workers since 2004, securing billions of dollars in verdicts and settlements, including some of the largest in U.S. history. The firm’s attorneys have considerable experience in maritime law, offshore safety regulations, and the complex liability issues that arise when employers fail to provide safe working environments. From oil rig accidents to vessel injuries, Arnold & Itkin stands with workers against negligent companies. No matter what.