Boil water advisory in the Utrecht region (2025): 5 lessons for drinking water companies

What happened

During a routine check, the drinking water company found the enterococcus bacterium in a drinking water reservoir in Utrecht. As a precaution, a boil water advisory applied to parts of the city of Utrecht and surrounding places, including Bilthoven, Bunnik, De Bilt, Maarssen and Zeist. This involved around 85,000 households and businesses, who had to boil the water for several days before using it.

The likely cause was damage to the cover of the reservoir at Kanaleneiland, which allowed slight contamination to occur. The advisory remained in force until successive clean water samples showed that the water was safe again. There was considerable unrest on social media and bottled water quickly sold out in supermarkets.

Lesson 1: Communicate quickly and by area

With a boil water advisory, every hour counts. After all, people use their tap water throughout the day. The drinking water company must therefore make clear within a few hours which postcodes or municipalities are affected, what is going on and what people should do.

One pitfall is communicating too broadly or too vaguely. Warning an entire service area when only part of it is affected causes unnecessary unrest and stockpiling. So work with a clearly defined area and the same message across all channels: your own service status map, the regional broadcaster, the municipalities and, if necessary, NL-Alert.

Lesson 2: Give concrete guidance on what to do

Above all, people want to know: what can I still do and what not? A good boil water advisory is very concrete about this.

• Boil water that you drink or use for coffee, tea, ice cubes, brushing your teeth and baby food for at least three minutes.
• Showering, washing up, doing the laundry and flushing the toilet can continue as normal.
• In doubt? Then use bottled water or boiled and cooled water.
• Repeat the core message unchanged on every channel, so that no confusion arises.

Lesson 3: Reach vulnerable and healthcare customers separately

A general message does not reach everyone in time. Hospitals, nursing and care homes, day nurseries, dialysis centres and the hospitality sector need specific information and sometimes extra measures. So approach these customers separately and as a priority, for example through a targeted email or phone call.

To do this, keep an up-to-date list of vulnerable and critical customers in advance. In practice, that list is difficult to compile during a crisis. Those who have this in order as part of their preparation gain valuable time.

Lesson 4: Manage expectations about lifting the advisory

A boil water advisory is only lifted once successive water samples are clean. Because a culture usually takes around 48 hours, an advisory can remain in force for several days, even when the source has already been dealt with. Explain this in advance, so that people understand why it cannot be lifted immediately.

Communicate actively in the meantime: which steps have been taken, when there will be news and where people can find the latest situation. In this way you keep control and prevent rumours from shaping the picture. Lift the advisory through exactly the same channels on which you issued it.

Lesson 5: Know your reporting obligations (NIS2 and CER)

Drinking water companies are critical entities. Since 15 August 2026, two laws have applied alongside each other: the Cybersecurity Act (NIS2), which concerns digital resilience, and the Critical Entities Resilience Act (CER), which concerns physical and all-hazards resilience. An incident that significantly disrupts your services must be reported within 24 hours to the competent authority.

Specifically for water quality, the Drinking Water Act applies: you report an exceedance of a standard to the Inspectie Leefomgeving en Transport (ILT). During the crisis, record which reports were made when and to whom. This is not only mandatory, it also helps with the evaluation afterwards.

How CrisisRadar helps

CrisisRadar brings your emergency team, municipalities, the GGD and the ILT together in a single shared crisis picture. You record facts with their source, draw up a boil water advisory and a Q&A within a few minutes, reach vulnerable customers in a targeted way and publish the current status on your own recognisable status page. The reporting-obligation timers keep track of which report is due when.

Would you like to see what such a boil water advisory crisis looks like step by step in the platform, from situational assessment to the public status page? Then take a look at the accompanying practice scenario.

Stappenplan

Veelgestelde vragen

How long should you boil the water during a boil water advisory?

Bring the water to the boil and let it boil for at least three minutes. Use this boiled and cooled water for drinking, coffee, tea, ice cubes, brushing your teeth and baby food. Showering, washing up and flushing the toilet can continue as normal with tap water.

Why is a boil water advisory not lifted immediately?

A boil water advisory is only lifted once successive water samples are clean. Because a culture takes around 48 hours, the advisory can remain in force for several days, even when the cause has already been resolved.

Which reporting obligation applies to drinking water contamination?

You report an exceedance of the quality standard under the Drinking Water Act to the Inspectie Leefomgeving en Transport (ILT). As a critical entity, you must also report a significant disruption within 24 hours under the Critical Entities Resilience Act (CER); cyber incidents fall under the Cybersecurity Act (NIS2).