Tap water in Greece: what the drought is changing in the network

273 microsiemens per centimetre is what the supplier measures in the Chania area of Crete, plus 13.7 mg/l of chloride, both on 15 June 2026. Athens comes in at 331 microsiemens and 9.5 mg/l. Two practically identical water qualities, and one of them comes from an island. This is where the rule of thumb that you should reach for bottled water on the islands falls down.

The dividing line follows the source of the water. Where a municipal water utility (DEYA) draws from karst springs, the water is low in salt and clean. Where it pumps from wells near the coast, the salt content rises as soon as the groundwater level falls. The boundary runs right through the middle of Crete and right through the middle of Kos.

Six chloride exceedances and one for sodium carry the same coding in the suppliers' laboratory portal. The portal requires three entries: cause, corrective action and time frame.

The cause entered there is Παρατεταμένη ξηρασία, prolonged drought. The measures noted are steps to tackle the cause, and in Heraklion also a change of water source. The time frame is long-term, which the portal defines as more than one year.

The mechanism is geologically simple. If the rain stays away, the groundwater level in the coastal wells drops. The pressure against the sea eases, and salt water moves in.

What the suppliers did not enter is also revealing. The portal has four levels of consumer instructions, from a recommendation to boil water to a ban on use; none of them has been set. Chloride and sodium are indicator parameters for taste and strain on materials, not a health risk. Water with 550 mg/l of chloride tastes salty and makes no one ill.

Twelve rows, one picture: the table brings together what the suppliers have most recently published. The “date” column gives the date of sampling.

The supplier reports the Cretan hardness values in French degrees; in the table they have been converted. Some of them come from earlier sampling than the conductivity and chloride values in the same row.

38,156 measurements for residual chlorine, 8,140 for E. coli and enterococci, 4,493 for pH and conductivity: Athens is the most densely monitored place on this topic. The Athens water supplier (EYDAP) has published a test report on this for 2025. The annual means:

• Nitrate 0.83 mg/l against a limit of 50, one of the lowest values among European big-city suppliers
• Lead 0.57 µg/l against a limit of 10, nickel 0.68 against 20, copper 7.3 against 2,000
• Trihalomethanes 24.7 µg/l against 100 and haloacetic acids 19.5 against 60, by-products of chlorination
• Per- and polyfluoroalkyl substances (PFAS), sum of 20 compounds: 0.02 µg/l against a limit of 0.10
• Bisphenol A was not detectable in 25 samples
• Hardness 150 mg calcium carbonate per litre, i.e. 8.4 degrees of German hardness
• Conductivity 331 µS/cm, pH 7.8, turbidity 0.22 turbidity units and aluminium 123 µg/l against a limit of 200

One value stands out because no limit applies to it: 6.8 nanograms per litre of geosmin. The substance comes from blue-green algae and soil bacteria, is harmless to health and causes the earthy aftertaste that some people notice in summer.

62 to 68 degrees of German hardness were measured at five sampling points in Corfu Town in May 2026, the highest hardness value in this article. The municipal supplier publishes every single analysis, more than 460 by now. All five sites give the same picture. Conductivity lies between 2,228 and 2,332 microsiemens, against a limit of 2,500. Chloride, by contrast, reaches only 30.1 to 46.5 mg/l, nitrate 8.1 to 12.9, residual chlorine 0.3 to 0.4. Coliform bacteria, E. coli and enterococci are at zero.

High conductivity with low chloride means dissolved limescale rather than seawater. Corfu is a karst island: the water runs through limestone and picks up calcium and magnesium. In Germany, the “hard” range starts at 14 degrees, and Corfu is at four times that. As a result, kettles scale up within days, and coffee and tea taste flat. You can still drink the water, though. What limescale does is explained in the guide to limescale in water.

Four districts on Kos exceed at least one limit value in the 2024 annual analyses. The supplier released the figures in May 2025; they are the only ones in this article with an exceedance for a health-related parameter:

• Kamari: arsenic 12 µg/l against a limit of 10. Kefalos shows 8.2.
• Antimacheia: nickel 29 µg/l against a limit of 20
• Kardamena: sulphate 359 mg/l against 250 and manganese 52 µg/l against 50
• Mastichari: chloride 288 mg/l against 250

The arsenic value deserves the most attention because you cannot taste it. Kos is part of the volcanic arc of the Aegean, and arsenic occurs naturally in rock of this kind. The limit of 10 µg/l applies to lifelong daily intake, not to a two-week holiday. How heavy metals get into water is explained in our guide to heavy metals in tap water.

On Kos, the supplier reports hardness directly in German degrees. The range extends from 11.1 in Kamari to 36.4 in Mastichari.

3,483 times in three months, the existing article was shown for questions about Rhodes, more often than for any other place except Crete. Even so, there are no reliable current figures. The website of the responsible supplier is protected by an automatic visitor check. In the national laboratory portal, Rhodes has three sampling points in Ialysos, whose most recent values date from November 2021.

For November 2021, the following can be said: conductivity 948 microsiemens, pH 8.3, coliform bacteria, E. coli and enterococci not detectable. That says nothing about 2026, which is why we would rather record the gap than estimate a figure. If you are travelling to Rhodes, ask your accommodation for the latest analysis.

461 times in three months, the existing article appeared for the question of whether you can brush your teeth with tap water in Greece. Not once was it clicked. The demand breaks down by island: 145 times for Crete, 34 for Kos, 33 for Corfu, 17 for Rhodes.

Brushing your teeth with tap water is safe at every place in this article. It is the least demanding use of all: the water stays in your mouth for seconds, and the amount swallowed is in the millilitre range. The only decisive factor would be the microbiological quality, and it was unremarkable at every sampling point. Even the salty Hersonissos value does not change that.

Caution is advisable for other reasons: with a private well not monitored by the municipality, when the accommodation has stood empty for weeks and when the water is visibly cloudy. A country where the question of risk is justified is covered in the guide to tap water in Turkey.

An activated carbon filter can do two things in Greece, but not a third. It removes chlorine, along with its smell, from the water and binds taste compounds such as geosmin. In a country with a legal minimum chlorine content, that is the obvious use. How it works is explained in the guide to the activated carbon filter for water.

It does not, however, remove salt. The 550 mg/l of chloride in Hersonissos passes through any activated carbon, because dissolved salts do not adhere to it. That would require reverse osmosis. The hardness also remains unchanged.

When travelling, a filter is worthwhile in three cases. It helps on trips with a motorhome or boat and during longer stays in accommodation with unknown plumbing. The third case is the chlorine taste. For short hotel stays in Athens, the measured values make the effort hard to justify. A mobile Alb Filter fits most taps and helps where the pipework beyond the house connection is unknown.