The impact of the WHO Guide to Ship Sanitation on water sampling

Practical tips for on-board water sampling
In theory, following the WHO’s recommendations sounds straightforward: test annually, document results and keep your records in order. But in daily operations the details matter, and small oversights can easily lead to big disruptions. To avoid issues and stay aligned with international health regulations, these pointers may be of help:

1. Know what applies to your ship
   Flag states differ. For example: some require testing for turbidity or specific bacteria strains, others do not. Not all labs keep an up-to–date overview of regulations per flag stage, so make sure you get your facts straight and maintain control of the sampling process.
   
   
2. Use consistent sampling points
   Make sure to take representative samples. The WHO recommends always sampling both at the tank (source) and the furthest point in the system. This provides insight into the condition of the distribution line; a common site for biofilm buildup or disinfectant loss.
   
   
3. Be mindful of risk points
   Showers, medical taps, or rarely used outlets are potential hotspots for Legionella or Pseudomonas aeruginosa. WHO recommends sampling at one showerhead without cleaning the hose, to assess actual risk.
   
   
4. Measure and document on-site values
   Before the sample reaches the lab, measure pH, free chlorine, conductivity, turbidity and temperature. These can shift during transport, so missing this step makes results harder to interpret.
   
   
5. Avoid wrong references
   Water reports should reflect maritime standards — not land-based drinking water norms. Align with flag state specifications and ensure your lab uses methods compliant with ISO/IEC 17025.
   
   
6. Keep track of previous results
   One elevated reading is often not a problem, but repeated patterns might suggest early signs of system issues, like chlorine loss or biofilm growth. Comparative data helps you discover issues, before they affect safety or documentation.
   
   
7. Use a lab familiar with maritime reporting
   Labs that know their way around the maritime industry have an advantage compared to general labs. A specialist lab can quickly select the right test parameters aligning with flag state requirements, ensuring your report matches the expectations of the inspecting party.