Why is it not recommended to drink tap water?

Drinking water is essential for human life and sustainable development. It is vital for health, hygiene, industry, and more. Yet, access to safe and clean drinking water remains a major challenge for many communities worldwide.

For example, tap water quality can be affected by various factors, such as microbiological or chemical contamination, or heavy metals. Ageing infrastructure is also a concern. In this article, we explain why drinking tap water may sometimes be inadvisable and explore alternatives to ensure safe drinking water at home.

Tap Water Contamination Issues and Associated Health Risks

Although tap water flows freely in households, its quality can occasionally be compromised, exposing consumers to health risks. The main types of contaminants are:

Chemical Contaminants

The French Agency for Food, Environmental and Occupational Health & Safety (ANSES) recently conducted a study on the presence of chemical contaminants in tap water in France.

The results are concerning:

• Pesticides and pesticide metabolites: 89 out of 157 were detected at least once in raw water, and 77 in treated water.
• Explosive residues: 54 substances were found.
• Solvents: 1,4-dioxane was detected in 8% of samples.

Long-term exposure to these contaminants can naturally have harmful effects on residents' health.

Effects of Pesticides and Their Metabolites in Tap Water

Pesticides undergo a journey before ending up in tap water. Their presence can affect the nervous system, impair cognitive functions, and increase the risk of Parkinson’s disease. There are also impacts on the endocrine system, including hormonal disruptions, early puberty, and reproductive disorders.

The risk of certain cancers is also increased, particularly lymphoma and prostate cancer.

Consequences of Explosive Residues in Tap Water

Groundwater contamination from explosive residues, the source of tap water, poses risks to the nervous and reproductive systems. Consumption can lead to:

• Developmental disorders
• Tremors
• Seizures
• Reduced fertility
• Birth defects

There is also a higher risk of liver and bladder cancers.

Effects of the Solvent 1,4-Dioxane in Distribution Water

1,4-Dioxane is an industrial solvent used in many products, including cosmetics, detergents, and pesticides. Exposure, even at low levels, can be harmful, causing:

• Cancer: Classified as a probable human carcinogen by the International Agency for Research on Cancer (IARC). Linked to increased risks of liver, kidney, and lung cancer.
• Respiratory problems: Inhalation can irritate airways, leading to bronchitis or emphysema.
• Reproductive issues: May affect fertility and foetal development.
• Nervous system damage: Can cause headaches, dizziness, fatigue, and concentration problems.

Biological Pollutants

Generally, tap water quality in most parts of Europe can be trusted, but it is not always free from harmful microorganisms. Biofilms—colonies of microorganisms that accumulate on pipe walls—can encourage bacterial and germ growth.

Two categories of germs are present in drinking water: those that thrive in water and those that survive in it.

Germs That Thrive in Tap Water

Examples of bacteria capable of living in tap water include:

• Legionella: Causes Legionnaires’ disease and thrives in biofilms within hot water pipes. Their growth is favoured by temperatures between 25 and 55°C, making unused old pipes a hotspot.
• Pseudomonas: Found in damp environments, these bacteria can cause urinary, pulmonary, intestinal, and skin infections. They are often resistant to many antibiotics.

Germs That Survive in Tap Water

Bacteria and viruses that can survive in tap water (at least temporarily) include:

• Coliform bacteria: Presence of Escherichia coli (E. coli) indicates recent faecal contamination. Consuming contaminated water may cause diarrhoea.
• Enterococci: More resilient than coliforms, they can survive for weeks, causing urinary and heart infections, as well as abdominal wounds and abscesses.
• Salmonella, Enterobacter, Cholera: Pathogenic bacteria that can survive in water and cause serious illness.
• Norovirus, Rotavirus: Viruses causing gastroenteritis, transmitted through drinking water.
• Hepatitis A and E: Can also be contracted from contaminated water.

Heavy Metals

Drinking water contaminated with heavy metals can have devastating health effects. Metals like mercury, lead, cadmium, and arsenic enter water through industrial activity, agriculture, and waste disposal.

Lead, cadmium, and arsenic are proven carcinogens. Other public health risks include:

• Increased risk of heart attacks, strokes, and high blood pressure.
• Acute or chronic kidney failure.
• Higher risk of developing type 2 diabetes.
• Damage to the brain, spinal cord, and nervous system, affecting learning, memory, behaviour, and motor skills.
• Weakened bones and increased fracture risk.
• Reproductive problems, including reduced fertility and birth defects.

Some individuals are more vulnerable than others. Children’s developing bodies are more sensitive to heavy metals, while the elderly often have weaker kidneys and immune systems.

Limitations of Water Treatment and Distribution Systems

Although French tap water is generally monitored and meets drinking standards, it can be affected during transport and storage in pipes.

Some limitations of water treatment systems include:

• Old materials: Cast iron and cement pipes in older networks can release metals (lead, copper), weaken infrastructure, and increase leaks and microbial contamination.
• New materials: Organic materials like PVC, polyethylene, and polypropylene are easier to install but can still influence water quality.
• Ageing networks: Corrosion and biofilm formation reduce disinfectant efficiency (chlorine) and promote microbial growth.
• Water stagnation: Can degrade taste and odour, reduce residual chlorine, and increase microbial growth.
• pH adjustment: Water is usually slightly alkaline (7–9) to limit scaling, but pH variations from dissolved CO2 can affect biofilm formation.
• Residual organic matter: Untreated organic matter can feed microorganisms in the distribution network.
• Disinfection: Chlorine or chloramine reduce microbial risks but may react with organic matter to form potentially harmful by-products.

In France, strict regulations ensure water safety from source to tap. Regional public health agencies conduct rigorous sampling and testing. However, growing pollution, ageing infrastructure, and evolving water treatments can expose limitations, with some by-products’ long-term effects not fully known.

Public Perception and Distrust

While most French people still drink tap water, consumption has been declining since 1995.

According to a survey, reasons include unpleasant taste, odour, and colour issues, such as reports of coloured water in Saint-André-de-Sangonis near Montpellier.

Some non-drinkers believe these issues are nationwide, often citing scandals where major water companies allegedly hid chemical and bacterial contamination.

Distrust also fuels concerns about water pollution and transparency, with some thinking treated wastewater is returned to taps.

If in doubt, contact your regional health agency (ARS). Water quality can vary by region or even by neighbourhood, depending on the source, treatment, and network condition.

Alternatives to Tap Water

Various options exist to address tap water quality limits, including bottled water and home filtration systems.

Bottled Water

Bottled water may be necessary in areas where tap water is unsafe. While safe in most of France, rural areas can have agricultural contaminants.

For daily consumption, tap water is usually the better choice. Bottled water can contain microplastics and occasionally fail quality standards. Production consumes energy and resources, generates plastic waste, and costs more than tap water.

Home Filtration Systems

Home filters use various technologies to remove impurities, including:

• Reducing contaminants like chlorine and persistent PFAS pollutants.
• Improving taste and odour.
• Softening hard water.
• Preserving essential minerals.

Activated carbon filters are common, absorbing organic impurities like chlorine, pesticides, and chemicals. Weeplow filtration systems come in various sizes to provide sufficient daily drinking water.

Adopt Good Practices to Drink Tap Water Safely

French tap water is usually strictly monitored and meets high drinking standards. Still, consumers should remain vigilant and take measures to ensure quality.

Maintain taps and pipes, as poor condition can contaminate water. Given bottled water’s environmental impact, filtered tap water is the preferable choice.

Explore our range of gravity filtration systems to find a solution that lets you drink tap water with confidence.