We drink water every day without thinking about it, and this is generally a good sign: it means we trust it. The water of the large Greek water supply networks is systematically tested and the published results justify this. However, this does not mean that the issue of «water and health» ends at the Athens tap. The quality of drinking water changes from region to region, from network to network, and even from apartment building to apartment building, depending on the source, the pipes and maintenance.

So it's worth knowing what your tap water may actually contain, where the legal limits lie, when there is cause for concern, and what a filter can, and cannot, do.

Who controls the water we drink?

Drinking water in the European Union is governed by Directive (EU) 2020/2184, which defines in detail the parametric values for dozens of substances: microbiological parameters, chemical compounds, heavy metals. In Greece, water providers, such as EYDAP in Attica, they regularly publish analysis results.

The main conclusion from the public data is reassuring: in the network of large cities the water meets the limits. The real questions begin where the central control ends: in the boreholes and local networks of the region, in the old internal piping of the buildings, in the tanks of the summer houses, and in the chlorination that is necessary but leaves its mark.

Chlorine: the necessary "guardian" with side effects

Chlorine is the reason tap water is microbiologically safe: it neutralizes pathogens all the way from the refinery to the tap. No serious scientist recommends tap water without disinfection.

But chlorine has two practical drawbacks. The first is known to anyone who has filled a glass in certain areas: taste and smell. The second is less visible: when chlorine reacts with natural organic matter in water, disinfection by-products are formed, most notably trihalomethanes (THMs). Directive 2020/2184 sets a limit of 100 μg/L for all THMs. It even asks providers to aim for lower values where possible, because long-term exposure to high concentrations has been associated in epidemiological studies with increased health risks. The World Health Organization covers disinfection byproducts in detail in its drinking water guidelines.

Simply put: chlorine needs to do its job in the network. But it doesn't need to reach the glass, and this is where activated carbon does its job: it traps chlorine and improves taste and odor at the point of use.

Nitrates: the silent issue of rural areas

Nitrate ions reach the water mainly from fertilizers and livestock waste and mainly concern boreholes and local networks in rural areas. They are invisible, odorless and do not change the taste, which is why they are insidious.

The limit in European legislation is 50 mg/L. The reason the limit is strict is mainly for infants: at high concentrations, nitrates are converted in the body into nitrites, which reduce the blood's ability to carry oxygen (methemoglobinemia, the so-called "blue baby syndrome"). This is why water used for infant formula in areas with boreholes deserves special attention.

If you live in an area with intensive farming and your water comes from a borehole or a small local network, a chemical analysis in an accredited laboratory is the most appropriate first step. If elevated nitrates are confirmed, there are cartridges specifically for nitrate retention, in addition to basic filtration.

Microbes: when does water become truly dangerous?

The most serious threat that drinking water may pose internationally is not chemicals, it is pathogenic microorganisms: coliform bacteria of fecal origin such as E. coli, salmonella, enterococci. .

In large networks, such incidents are rare and usually local: a pipeline failure, work, a pressure drop that allows suction, a tank that has not been cleaned. In summer cottages with tanks or wells, in boreholes without regular inspection and in small networks with old infrastructure, the microbiological risk is more real. The symptoms of a waterborne infection are usually gastrointestinal and in healthy adults they pass, but in infants, the elderly and the immunocompromised they can develop seriously.

It's worth noting here how filtration works: a ceramic filter acts like an extremely fine sieve. On the 0.5 to 0.1 micron scale, it traps particles the size of bacteria, which is why quality ceramic filters are lab-tested specifically for bacteria retention.

Heavy metals: the problem is often inside the building

Even when water leaves the network clean, it can "load" the last part of the journey: the pipes of the building itself. In old structures with lead pipes or old solder, lead can pass into the water, especially in the first water of the morning that has been stagnant in the pipes overnight.

Lead is one of the most studied toxic substances: it affects the neurological development of children even at low concentrations, which is why legislation is constantly tightening. Directive 2020/2184 currently sets a limit of 10 μg/L, with a provision to reduce it to 5 μg/L by 2036. Practical advice that costs zero: in old buildings, let the water run a little in the morning before drinking, and for drinking and cooking, always prefer the cold tap.

And the cruelty? Annoying yes, dangerous no

"Hard" water, that is, water with a lot of calcium and magnesium salts, is one of the most frequently asked questions. The answer from science is rather comforting: hardness is not a health hazard. Calcium and magnesium are nutrients. Hard water mainly affects devices and resistors, not the body. If you are interested in the subject in detail, there is a complete guide to water hardness by region of Greece.

Here lies an important detail about filters: a proper tap filter does not remove mineral salts and trace elements. It retains unwanted substances, chlorine, microbes, particles, and leaves the water "alive". Complete desalination is the work of another technology (reverse osmosis) and only makes sense in specific cases, such as heavily contaminated borehole water.

What a water filter does and doesn't do

Let's be clear, because the market is filled with exaggerations in every direction:

What a quality point-of-use filter offers: chlorine retention and taste and odor improvement, retention of particles, rust and microplastics, and, in ceramic filters with certified control, retention of bacteria at the micron scale. With special cartridges, targeted retention of salts or nitrates where needed.

What it doesn't do: It does not replace public water control, it does not "cure" unsuitable well water without prior analysis, and it does not need to promise magic. And something that is not often said: a filter that is not properly maintained can itself become a hotbed of germs, which is why changing the cartridge on time is not a detail, it is part of hygiene.

The Greek answer to the problem of microbes in the filter

The last point, the microbes inside the device itself, is the most interesting part of Greek research in the field. OLYMPUS+ antimicrobial water filter, designed and manufactured in Acharnes by Center Plus SA, is a patented global innovation in its category: in addition to the ceramic filter and activated carbon, it incorporates parts made of antimicrobial copper alloy (CW606N and CW508L, registered with the US EPA).

The idea is simple: copper doesn't "filter," it kills. The copper ions that are continuously released destroy the cell membrane and DNA of microbes on contact surfaces, permanently disinfecting the inside of the device, what the company calls self-disinfection. According to the manufacturer, the system kills up to 95% of microbial flora inside the device within 2 hours.

But the most important thing is the documentation: the retention of bacteria was tested by the Agricultural University of Athens (2010), while the antimicrobial activity inside the device was studied for 12 consecutive months by the Microbiology Laboratory of the Medical School of the University of Athens, along with tests by 3 certified European chemical laboratories. Among the microorganisms retained by the filtration system: E. coli, salmonella, fecal coliforms, staphylococci, enterococci. .

Practical guide: what to do depending on your situation

• You live in a big city with mains water: your water is microbiologically tested. If you are bothered by the chlorine taste or want an extra level of assurance for particles and germs, a Countertop filter (from 77€) or a token Undersink filter covers the point of use.
• Water from a borehole or small local network: Start with chemical and microbiological analysis. Depending on the findings, you choose the solution, from simple filtration to special nitrate or salt cartridges.
• Infant at home: Be careful with nitrates if you are not on a large network, and be consistent in maintaining any filter you use.
• You don't know where to start: a short one guide to selecting the right filter and the model selection tool they help you find what suits your own water and home.
• You already have a filter: set a reminder for ampoule. Olympus water filters are replaced every 12 months or 8,000 liters, whichever comes first.

Frequently asked questions

Does Athens water need a filter?; From a safety perspective, not necessarily: EYDAP water is systematically tested. The filter here offers better taste without chlorine, protection from particles and rust in the pipes, and an additional microbiological safety net at the point of use.

Does the filter remove the calcium and magnesium I need?; No. The ceramic activated carbon filter retains chlorine, particles and microorganisms, but allows the passage of mineral salts and trace elements. Salt retention is provided by double/triple water filters and reverse osmosis.

How often is the cartridge changed?; For Olympus filters, up to 12 months or 8,000 liters, whichever comes first. Regular replacement is essential regardless of brand: a forgotten cartridge stops protecting.

Isn't boiling enough?; Boiling kills germs but does not remove chlorine, nitrates, heavy metals or particles, and is not practical for every glass. It is an emergency solution, not an everyday strategy.

Bottled or filtered tap water?; For most families on mains water, filtered tap water offers comparable quality at a fraction of the cost and without plastic bottles. Bottled water retains its role for travel and in areas with substandard water.

Sources: Directive (EU) 2020/2184 on the quality of water intended for human consumption; WHO Guidelines for Drinking-water Quality (4th edition); published EYDAP quality data; Center Plus SA technical documentation (olympusplus.gr).

John Giotis

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