ISSUE 12 | MARCH-APRIL 2025 42 HEALTHY HABITS while other international standards outline the sanitary design of ship water supplies and potable water quality assessments. Key considerations for potable water safety Improper management of water can serve as a direct route for infectious disease transmission on ships. Most waterborne outbreaks on vessels occur when water is contaminated with pathogens from human or animal waste. While chemical contamination is less common, it can still pose a risk. To safeguard the health of passengers and crew, potable water on ships must be protected by multiple layers of safety measures. This “multiple-barrier system” spans from the water source on shore, through the ship’s distribution system, treatment, and storage, and finally to each water supply outlet. These barriers prevent contamination throughout the entire process. Even if the water at the port of origin is deemed safe, it is not guaranteed to remain safe once it enters the ship’s systems. An understanding of the entire drinking-water supply chain aboard the ship helps to pinpoint potential contamination risks at each stage of the process. Waterborne disease outbreaks have been linked to poor-quality bunkered water, underscoring the importance of ensuring the water taken onboard meets safety standards. Drinking water supply management ●● Drinking water storage tanks must be cleaned and disinfected at least once every two years, or more frequently if contamination is detected through testing. This process should occur during dry or wet docking. ●● Drinking water loading hoses should be thoroughly flushed before each use and disinfected at least every six months. The hoses should be stored properly, with caps to prevent contamination. ●● Shipowners are responsible for ensuring that drinking water taken on board meets the required quality standards. Regular monitoring, in line with the WHO Guide to Ship Sanitation, should be conducted to confirm that the water is free from microbial and chemical hazards. ●● Drinking water on board can be tested using portable test kits, and a water quality report should be available before taking on water at any port. Freshwater onboard large ocean-going vessels serves multiple purposes. Not only is it used for drinking and food preparation, but it also plays a vital role in protecting the ship’s plumbing and fixtures from corrosion, which can be caused by exposure to saltwater. WATER QUALITY AT SEA: BEST PRACTICES FOR POTABLE WATER ON SHIPS While it is ideal to have a single water system that supplies potable water for drinking, food preparation, dishwashing, sanitation, and laundry, there are instances where two or even three separate systems may be required. The storage and distribution of potable water aboard vessels presents a unique challenge, particularly in a confined environment. Proper management is critical to prevent bacterial contamination and ensure the water remains safe for consumption. All nonpotable water outlets must be clearly marked with labels such as “UNFIT FOR DRINKING.” It is crucial that there is no direct connection between the potable and non-potable water systems, unless an appropriate backflow-prevention device is in place to prevent contamination. Regulatory guidelines The ILO Convention C133 (Accommodation of Crews [Supplementary Provisions] Convention, 1970) sets minimum standards for potable water provision and has been ratified by many countries. Similarly, the MLC, 2006, provides comprehensive protections for seafarers, consolidating over 65 international labour standards relating to seafarer welfare, including provisions for drinking water on board. The IMO Life-Saving Appliance Code (2010) also addresses potable water requirements for rescue boats,
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