Contaminated drinking water: Illness from tap water?

People can become ill from contaminated drinking or tap water.

Contaminated drinking water refers to water containing pathogens or other components in a concentration that is hazardous to human health.

Drinking water hygiene as a decisive factor

As long as the regulations and requirements for impeccable drinking water hygiene are met, it can generally be assumed that tap water in the UK is fit for human consumption.

In the UK, draw-off points of installations from which no drinking water is provided must also be permanently and clearly marked in accordance with The Water Supply (Water Fitting) Regulations. This is intended to prevent this water from being used accidentally for drinking, cooking or personal hygiene.

When does tap water become a danger?

Tap water is used not only for drinking and cooking, but also for personal hygiene, cleaning objects in contact with food, and other domestic purposes. An illness or infection can therefore occur orally, via wounds, or through the inhalation of fine water droplets (aerosols).

It can become critical if the concentrations of certain microorganisms increase due to a lack of drinking water hygiene (for example, stagnation in drinking water pipes, unsuitable temperatures for cold or hot water, etc.) or technical defects.

Specifically, the following pathogen groups should be mentioned:

• Legionella: These bacteria multiply ideally in warm stagnant water and can trigger severe infections when aerosols are inhaled. You can find out more at: Legionella in water: prevention and control.
• Pseudomonads: The germ Pseudomonas aeruginosa is particularly feared in medical facilities, as its strong antibiotic resistance makes it one of the dangerous hospital germs. You can find details here: Pseudomonads in drinking water.
• Coliform bacteria and E. coli: These are considered indicators of contamination and must not be detectable in drinking water. Everything about this at: Coliform Bacteria: E. coli, Enterobacter & more.

Our article Bacteria and germs in drinking water: What you need to know provides a general overview of potential pathogens in drinking water.

Symptoms: Illness from tap water

The symptoms of contaminated tap water depend heavily on the respective pathogen. Signs can include:

• Gastrointestinal complaints (typical for faecal contamination)
• Fever and flu-like symptoms (often with Legionella infections)
• Wound infections
• Inflammation of the respiratory tract

Corresponding symptoms do not necessarily indicate an illness caused by drinking water, and clarification by a doctor is essential.

How high is the risk of becoming ill from tap water?

In the UK, the standards are governed by the Water Supply (Water Quality) Regulations 2018 (noting regional variations in England, Wales, Scotland and Northern Ireland), ensuring the safety of drinking water installations. This ensures high drinking water quality. Generally, the quality of drinking water is therefore very high and the risk of illness is to be assessed as rather low.

However, people with a weakened immune system have a higher risk of becoming ill from contaminated water – meaning that the topic of drinking water hygiene takes on even greater significance, especially in healthcare facilities such as hospitals or care homes.