Coffee or tea above the clouds? Why you should be careful with water hygiene on aircraft

A freshly brewed coffee or a cup of tea is part of the flight experience for many travellers. However, current studies show: water quality on aircraft often fails to meet strict hygiene standards.

Learn why hot drinks prepared on board pose risks, how you can protect your health and how airlines can ensure drinking water hygiene.

The invisible danger in the water tank

While drinking water in the UK is strictly monitored by the Water Supply (Water Quality) Regulations 2018, rules for aircraft – especially internationally – are often less transparent.

A current study by the Center for Food as Medicine & Longevity (2026) examined the water quality of 21 airlines in a total of 35,674 samples from various outlets such as galleys and toilets over a period of three years – with some concerning results.

The study rated airlines according to a point system, in which many providers failed due to systematic deficiencies.

The most critical results regarding drinking water hygiene on aircraft at a glance

Faecal contamination by E. coli: In a total of 32 cases, violations of the permitted limits for Escherichia coli were exceeded. As these bacteria are considered direct evidence of faecal contamination, this poses a significant health risk to all fellow passengers.

Deficient maintenance protocols: The study criticises that many airlines do not adhere to the prescribed intervals for cleaning, flushing and disinfecting their water tanks. Without these regular measures, biofilms can form in the tanks, in which germs can ideally survive or multiply.

Lack of transparency regarding limit values: Frequently, passengers were not informed in time when samples were negative. A consistent implementation of the obligation to inform, as provided for in the Water Supply (Water Quality) Regulations 2018, is often not present in international aviation.

Increased risk on regional flights: The situation is particularly alarming for smaller regional carriers. Here, the contamination with coliform bacteria was more than twice as high as with large airlines (4.75% compared to 1.89%).

Why heating often isn't enough for coffee and tea

Many passengers feel safe because the water for coffee or tea is heated. However, this is where a decisive problem lies: the water in the galleys is often not permanently brought to the required temperature to safely eliminate all germs.

Hygienic weak points in aviation are:

Complex infrastructure: Water is delivered to the aircraft via trucks and hoses. Every tank and every interface is a risk for contamination.

Stagnant water: Water can sometimes stand for long periods in the pipes and tanks of the aircraft, which promotes the growth of biofilms and / or the multiplication of pathogens.

Lack of maintenance: Cleaning and flushing of the tanks often only take place at long intervals, which can promote the colonisation of bacteria in the drinking water.

Our tips for handling drinking water on flights

• Original sealed drinks: Only choose water from sealed bottles or cans.
• Avoid hot drinks: Avoid coffee or tea if they have been prepared with the on-board tap water.
• Ice cube check: Ask whether ice cubes come from bottled water or from the on-board tank. If in doubt: "No ice, please."
• Hand hygiene: After washing your hands in the washroom, additionally use an alcoholic hand sanitiser, as the water in the on-board toilets is also frequently contaminated.

What airlines can do for drinking water hygiene

Prevention and the regular treatment of the entire water system are crucial:

• Compliance with strict maintenance intervals: Airlines should shorten the intervals for chemical disinfection and mechanical cleaning of the water tanks. This is the only way to remove deposits that serve as a breeding ground for bacteria.
• Professional disinfection solutions: The use of certified disinfectants ensures that even hard-to-reach pipe sections are cleared of germs. This is particularly important after long aircraft idle times, during which the risk of contamination increases significantly.

Airlines also have the opportunity to further increase safety for passengers and crew by using filter solutions:

• Certified bacterial retention: Through filters tested according to the international standard ASTM F838, bacteria are reliably retained. This sterile filtration ensures that pathogens do not enter the coffee machine or the kettle.
• Protection against air blockage and frost: Extreme pressure and temperature conditions prevail in aircraft. The use of permanent hydrophobic (water-repellent) membranes keeps the water flow stable even after frost periods or in the event of air inclusions.

Since every aircraft model has different requirements, Aqua free develops tailored filter solutions for drinking water that can be integrated directly into the existing systems of galleys and washrooms. Contact us!