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Published on 07/02/2022

How to Test Potable Water

Potable water is an on-board essential and has a variety of uses beyond being safe to drink.

Clean water is something we often take for granted on dry land – but at sea, carrying and managing water for drinking and everyday tasks like washing and cleaning poses more of a challenge. Safe, clean drinking water is essential cargo on board any sea-going vessel – but proper management is key in order to prevent ill health and ensure crew safety.

When stored for even short periods of time, even clean water can become a breeding ground for dangerous contaminants which can pose a risk to health and in some cases result in fatalities.

What are the dangers of untested potable water?

Potable water is an on-board essential and has a variety of uses beyond being safe to drink. Water on board is also used for washing, cooking and cleaning purposes – any water that comes into contact with the skin or items that will be close to food or drink must be potable.

But water can also contain dangerous contaminants such as bacteria and viruses that pose a significant risk to human health. Some of the most common biological or organic contaminants found in improperly treated and managed drinking water include:


*Legionnaires Disease





These bacterial infections and viruses don’t need to be consumed to pose a hazard to health – exposure to contaminated water through washing in it or even occupying the same space for a period of time can be just as dangerous. Legionnaires in particular is caused simply by breathing in microscopic bacteria from unclean or contaminated water.

Other potential contaminants of concern when managing potable water for marine vessels include physical, chemical, biological or radiological substances that enter the water stream before or during its time on board.

Sickness amongst crew members not only poses a significant risk to the health of each individual and those around them – it also impacts upon ship performance overall, compromising the crew as a collective and in turn increasing the risk of knock-on issues and potentially hazardous events.


The first defence against contaminated water on board is the proper management of water storage and distribution systems – but even with careful and considered supervision, contamination can still occur. Thoroughly and regularly testing potable water on board is the only way to be 100% certain that your potable water is safe to use at all times.

Testing is important because water may not look or smell dirty at first glance – but appearances can be deceptive. Even seemingly clean water can pose a microbial risk from any waterborne bacteria or contaminants it contains.

There are numerous opportunities for potential contaminants to enter a water supply on board any sea-going vessel – with improper storage and cross-contamination amongst the most prevalent.  

Risk factors that are commonly implicated in the contamination of potable water on board include:

*Inadequate cleaning and disinfection

*Poorly designed potable water storage tanks and containers

*Contaminated bunkered water

*Cross-connections between potable and unpotable water

*Poor water distribution design

*Human error (including unintentional introduction of contaminants)

*Compromised water distribution systems, or improper management of water distribution systems on board

Whatever the cause, issues that can often be traced back to improperly managed or contaminated water could be resolved quickly and safely with the regular use of a reliable potable water testing kit.


Although high incidences of gastrointestinal disease outbreaks continue to plague the shipping industry, potable water testing is remarkably quick and simple.

Using a specialist testing kit, water samples can be taken from water storage units and scanned for potential contamination, preventing illness or injury from occurring.

Tests usually involve a number of steps, which include taking a sample of water in a sterile container for testing, incubating the sample then using a special solution which causes the water to change colour depending on any contaminants present. Tests should be conducted at regular intervals, no less than once a week according to MLC 2006 guidelines. The WHO and HSE also have a number of resources and recommendations to ensure water safety on board.

It’s important to choose a kit that identifies all potential contaminants that may be present in the water to provide 360o protection for crew members. Some testing methods, such as test strips, will only reveal a partial picture of potable water cleanliness. The MLC recommends that a Fresh Water Safety Plan is implemented on board sea-going vessels to ensure that a regular testing schedule is in place at all times.

Martek Marine’s innovative potable water testing kits are amongst the most comprehensive on the market, with diverse testing range, simple operation and easy maintenance. We supply a variety of solutions tailored specifically for a wide range of marine applications.


At Martek Marine crew welfare and ship safety are amongst our top priorities. It’s impossible to over-emphasise the importance of clean, safe drinking water on board – which is why we offer a range of sophisticated solutions all designed to be simple to use and highly accurate ensuring full peace of mind and MLC 2006 compliance at all times. DrinkSafe and DrinkSafe Max have been developed with the highest levels of accuracy and ease of use in mind and are trusted by the world’s largest shipping companies.

Browse our potable water testing solutions or get in touch today for tailored support when selecting water testing kits.