Many questions arise when it comes to tap water: is it safe to drink or not? The debate quickly becomes heated, fuelled by fears of bacteria in the water, concerns about contamination and doubts regarding the water’s quality for human consumption.To shed some light on this topic, we asked Professor Patrizia Calella, a lecturer in General and Applied Hygiene at UniCamillus University, for her point of view. She provided a scientific yet straightforward explanation of what you really need to know.
Drinking water: what it really means and why it isn’t ‘pure water’
The first thing to clarify is the meaning of safety of drinking water, which is often misunderstood.
The professor explains that “when water is safe to drink, it means it is suitable for human consumption and can be drunk and used for food preparation without any health risks”, but this does not mean it is completely free of substances.
In other words, the safety of drinking water does not mean ‘sterile water’, but rather a balance controlled and regulated by European and national regulations. “Drinking water must be microbiologically safe—meaning free from pathogenic microorganisms—and chemically monitored so that any substances present remain within scientifically established safety limits. It must also be clear and free from any unusual odours or tastes”, explains Professor Calella.
Tap water and testing: a reality check
When it comes to contaminated water or waterborne bacteria, the key issue is monitoring.
The professor emphasises that “in Italy, tap water is monitored throughout the entire supply chain—from abstraction to distribution in households”. This includes not only periodic checks, but also a preventive system known as the Water Safety Plan, recommended by the World Health Organization and adopted in Italy as well. This system is designed to identify risks before they become problems. “From an analytical perspective, microbiological and chemical parameters, as well as quality indicators, are monitored”.
Which parameters are monitored?
Among the indicators examined are:
• absence of bacteria such as Escherichia coli and intestinal enterococci
• monitoring of indicator bacteria in the water
• testing for nitrates, lead, pesticides, PFAS (per- and polyfluoroalkyl substances) and disinfection by-products
• assessment of odour, taste and turbidity
This significantly reduces the risk of contaminated water.
Contaminated water: symptoms and when to be genuinely concerned
Fear of contaminated water and the symptoms it may cause is one of the most common concerns. In this regard, Professor Calella explains that if the contamination is microbiological, symptoms may include gastroenteritis, diarrhoea and vomiting, whilst in more serious cases more severe infections can occur in vulnerable individuals. In the case of chemical contamination, however, the problem is not immediate but linked to long-term exposure.
Legionella and water: the real risk is inside the home
Legionella in water is one of the most frequently discussed topics when it comes to water safety. In reality, Calella clarifies that “it is not accurate to say that Legionella is simply present or absent in domestic water”. The issue arises mainly within internal plumbing systems, not in the mains water itself.
The risk becomes more concerning in situations involving:
• prolonged stagnation
• lukewarm temperatures
• poor system maintenance
• biofilm formation
“This is why the ISS (Istituto Superiore di Sanità) and the ECDC (European Centre for Disease Prevention and Control) recommend keeping cold water below 20°C, hot water above 50°C, and avoiding prolonged stagnation”, our expert points out.
Tap water: is it worse than other sources?
Many people wonder whether tap water is worse than water from wells or springs. Professor Calella explains that “water from public water systems is subject to continuous monitoring, strict regulatory requirements and health surveillance throughout the entire supply chain”, whereas private sources (such as wells, springs or domestic collection systems) may be more vulnerable to contamination. “This does not mean they are necessarily of lower quality”, warns Calella. “A well or spring can provide excellent water, but it requires greater responsibility on the part of the user in terms of maintenance, protection of the surrounding area and regular testing”.
In particular, it is important to monitor for microbiological contamination, nitrates, metals and substances linked to agricultural or industrial activities. Water quality depends heavily on the environment it passes through as it moves through soil and aquifers.
Who needs to be most careful about waterborne bacteria?
The risks associated with waterborne bacteria are not the same for everyone. The most vulnerable groups are:
• infants
• older adults
• immunocompromised individuals
• people with chronic conditions
For certain infections, such as legionellosis, the risk increases in the presence of respiratory illnesses or conditions of clinical frailty”, says Calella. “In infants, however, it is also important to consider a specific risk that is not only microbiological but also chemical: high concentrations of nitrates in water can, during the first year of life, lead to methaemoglobinaemia—a rare but potentially serious condition that reduces the blood’s ability to carry oxygen”. For this reason, the guidelines recommend paying particular attention to the quality of the water used to prepare infant formula and baby food.
How to tell if water is contaminated?
If you suspect the water is contaminated, the first step is not to panic. Professor Calella recommends consulting the data provided by the water supplier, the local council or the local health authority (ASL/ATS). “In Italy, the regulatory reference is Legislative Decree 18/2023, which incorporates the European directive on water intended for human consumption and requires that information on water quality be accessible and up to date for citizens. Many water suppliers publish periodic reports with the main parameters (microbiological and chemical), often broken down by area or neighbourhood”.
Only in the event of specific, concrete concerns about the water (such as unusual odour, turbidity or colour) or about the domestic plumbing system should laboratory testing be carried out, particularly to check for any bacteria or chemical contaminants.
Filters and purifiers: are they really necessary?
Another much-debated topic when it comes to the safety of tap water is the use of filters. The lecturer explains that domestic systems can only be useful if chosen to address a specific problem and maintained correctly. “Activated carbon can improve taste and odour and reduce certain compounds; reverse osmosis reduces various contaminants but is more complex, requires maintenance and can excessively deplete the water if not managed properly; UV systems can help from a microbiological perspective, but they do not remove chemical contaminants. Therefore, domestic devices, if neglected, can themselves become a source of microbiological risk”.
So be careful: a poorly managed filter can worsen water quality and encourage bacterial growth. So ‘filtered’ does not always mean safer!”.
Daily precautions to reduce the risks of contaminated water
Professor Calella recommends:
• letting the water run for a few seconds after many hours of non-use
• cleaning aerators and filters regularly
• avoiding prolonged stagnation
• replacing domestic filters at the correct intervals
• not neglecting boilers or tanks
So… is tap water good or not? Let’s set the record straight
The answer to this question is quite clear. The professor explains that in Italy, tap water is generally safe and monitored in accordance with very strict European standards. “Our country applies European legislation on the quality of water intended for human consumption, with structured controls and a risk-based approach, in line with the recommendations of the World Health Organisation”.
“This system has been further strengthened by Legislative Decree No. 102 of 19 June 2025, which came into force in July 2025, updating and supplementing the previous legislation. The decree introduces stricter limits for certain emerging contaminants, such as PFAS, reinforces the preventive approach based on Water Safety Plans, and increases controls throughout the supply chain”.
One particularly significant development concerns the focus on internal plumbing systems within buildings. “The decree extends the concept of safety right through to the point of use, introducing obligations regarding risk assessment and management, particularly in sensitive settings such as schools, hospitals and communal facilities. The key point, therefore, is this: safety standards are very high right up to the point of delivery, but part of the risk may depend on the internal plumbing system of the building or home”.The most accurate message, therefore, is neither alarmist nor naively reassuring: tap water in Italy is, in the vast majority of cases, a safe, economical and sustainable choice, provided that attention is also paid to domestic management and maintenance.