Faecal bacteria in tap water: risk and filter tips

Reading time: ~10 minutes

1. How often is there faecal bacteria in tap water?

Almost never. The hard figures are in the annual quality assessment by the Human Environment and Transport Inspectorate, summarised by Vewin: in 2023 the drinking water companies carried out 565,689 measurements across more than 60 parameters, and 99.9 percent of the samples met the legal standards. In 601 cases a standard was not met, and 24 of those cases involved enterococci or E. coli.

Twenty-four confirmed cases across an entire country in an entire year — that's the order of magnitude. We deliberately don't convert that into a percentage, because those 565,689 measurements cover more than 60 parameters together, not just microbiology. The RIVM states that Dutch tap water is so clean that you can drink it without worry, and that it contains no chlorine. That last point is exactly why those measurements matter so much: there's no disinfectant in the pipe to clean up a contamination along the way.

So why does it feel like it happens often? Because a boil-water advisory is news. A single pipe burst in one neighbourhood generates regional headlines, and that's a good thing, because that coverage is exactly how you get warned in time. At PureFilter we see those news days reflected in our own visitor numbers: suddenly people search en masse for what's in their tap water.

2. What exactly is the faecal bacteria?

The term is a media nickname. Where journalists write "faecal bacteria", the lab report says Escherichia coli, abbreviated to E. coli. Drinking water company WML writes that this nickname sounds pretty gross and immediately conjures up a certain image, while in practice things are thankfully somewhat different.

That distinction between pathogen and indicator is the core of the whole topic. The RIVM puts it this way: these bacteria shouldn't be in drinking water, healthy people usually don't get sick from them, but the same route can bring along bacteria, viruses and parasites that do. That's why any finding, however small, immediately leads to measures.

Enterococci are the second indicator that's routinely measured alongside it. They belong to the same contamination route but survive longer in water, which means they can point to an older contamination. How the two relate to each other and why they always appear together in the news is something we've worked out in our article on enterococci and E. coli in tap water.

3. How does the faecal bacteria get into drinking water?

Not at the source and not during treatment, but almost always in the pipe network. Waternet names three situations: a leak, a pipe left open for works, and a digger accidentally hitting a water pipe. At such moments, groundwater or sewage water can get in.

The RIVM summarises the same route as "during works or with a broken pipe, faecal matter from people or animals can end up in the drinking water". Drinking water company Vitens also explains that it's an incident in the network, not a structural quality problem.

What does this mean for your own pipework?

Behind your water meter, you're responsible yourself for the quality of your drinking water, writes Milieu Centraal. There, it's not about the faecal bacteria but about two other risks: legionella in standing hot water and lead from pipes installed before 1960. That's also the reason it's better not to drink standing or lukewarm water, something we explore further in our piece on drinking warm tap water.

4. How do you know if there's faecal bacteria in your tap water?

You can't see, smell or taste it. You find out because your water company tells you. There's no reliable home test for microbiology, and clear water says nothing: cloudy or brown water almost always has a different cause, usually iron or loosened particles after works.

Waternet checks dozens of spots in the network daily and informs people about a contamination by letter for a small area, and via the website, social media and news media for larger areas. If you're without water or dealing with a fault, our practical guide on what to do if no tap water comes out of the tap is a logical next step.

In short, this is the reliable route: no boil-water advisory from your water company means no contamination. Anyone who really wants to know the quality of their own pipework water should have a sample taken by an accredited laboratory, since that's the only method that can demonstrate the absence of these bacteria.

5. Boil-water advisory: what can you still do with the water?

More than people think. The RIVM is very precise about this: boil the water you want to drink for three minutes first, and all the pathogens are gone. Using unboiled water for showering, brushing your teeth or washing up isn't dangerous. A boil-water advisory is a precautionary measure and remains in place until checks show the water is clean again.

One important nuance: individual water companies can advise more strictly than that national line. Waternet, for example, does include brushing your teeth on the list of things for which you should use boiled water. So the rule is simple: your water company's advice always takes precedence over a general explanation, including this one.

Those three minutes aren't an arbitrary number, and that's immediately a pitfall with modern kitchen appliances. Water that briefly touches 100 degrees once isn't the same as water that boils for three minutes straight. Anyone with a boiling water tap who's wondering how filtration fits in can find the answer on our page about a water filter combined with a Quooker. During a boil-water advisory, always follow your water company's instructions, even if you have such an appliance.

• Boil drinking water, cooking water and water for baby formula for three minutes and let it cool afterwards.
• Also boil the drinking water for pets, since they're just as susceptible to the hitchhikers as people are.
• Showering, washing hands and washing up can continue as normal with unboiled water; check what your water company advises for brushing teeth.
• Throw away ice cubes made with the suspect water and make new ones with boiled water.
• Once the advisory is lifted, flush your taps and your filter thoroughly for a few minutes.

That last point explicitly applies if you have a filter system too. A filter is not a bypass to get around the advisory, and flushing afterwards is part of normal maintenance.

6. How quickly do you get sick from E. coli?

For most people, nothing happens. The RIVM writes that healthy people usually don't get sick from E. coli or enterococci themselves. If symptoms do occur, according to the same source they're usually gastrointestinal complaints. The RIVM makes no statement on this page about how quickly those would appear, and we're not going to fill that in ourselves.

The RIVM does explicitly state that the effects of contaminated drinking water can be serious for young children, the elderly, pregnant women and people with a weakened immune system. That's the reason a boil-water advisory is issued so broadly and so quickly, even when the risk is small. If you have symptoms after a boil-water advisory in your area, contact your GP. We don't give medical advice and shouldn't either.

7. Does a water filter remove the faecal bacteria?

No, and we need to be clear about that. An under-sink filter like the PureFilter Mineral+ is a chemical and mechanical filter, not a disinfection installation. The NSF/ANSI standards 42 and 53 that this type of system is tested against cover taste, odour and health-related substances, not microbiological safety. Separate certifications exist for that, including NSF/ANSI 55 for ultraviolet treatment and NSF/ANSI 244 for filters that reduce bacteria, viruses and parasites. So filtration can be microbiologically certified, but the Mineral+ hasn't been tested for that, and we don't claim it has.

So we don't sell a bacteria solution, and we don't claim to. During a boil-water advisory, boiling is the answer, regardless of which filter hangs under your sink. This table sets out what each approach actually does.

The table makes the division of roles visible. Boiling and UV solve microbiology but leave chemistry in place. A carbon filter does the opposite. If you want to understand the techniques behind those columns, our overview of which water filter suits you explains per method what does and doesn't come out.

8. What a water filter does remove from your tap water

This is where the real benefit lies, and it's a different problem than the faecal bacteria. According to Vewin, 534 of the 601 exceedances in 2023 involved substances without a direct public health risk. That same source does warn that the quality of the drinking water sources is under pressure from contamination from agriculture, industry and households, and hasn't improved significantly in recent years.

That's a trend that can't be solved neighbourhood by neighbourhood or week by week with a boil-water advisory. The PureFilter Mineral+ is built for exactly that: a 5-stage system that removes more than 100 contaminants by around 99 percent, including PFAS, microplastics, heavy metals such as lead and copper, fluoride, nitrate, medicine residues and chlorine. The system is NSF-certified under 42, 53, 61 and 372.

PFAS is the question we get most often, and it's also one of the questions Google itself shows alongside this topic. How these substances work and why they're so persistent is explained on our page about a water filter against PFAS.

The second part of the story is what comes back. Many filters strip out everything, minerals included. After filtering, the Mineral+ adds calcium, magnesium and potassium back via Swedish Mineral Rock™, which makes the water taste softer and fuller. So purifying and mineralising in a single pass.

9. Buying advice: where a filter makes sense

Don't buy a filter out of fear of a bacterium. Buy one because you want better-tasting, purer water every day from your existing tap, without refilling jugs or hauling bottles. That's a rational consideration, not a panic purchase, and it's exactly how we discuss this topic at PureFilter.

What determines the choice in practice is the replacement frequency and the capacity. A single €65.00 cartridge lasts up to 12 months and 15,000 to 20,000 litres, which over a full twelve months works out to less than one cent per litre. A filter jug requires thirteen swaps a year. If you're looking for a permanent water filter for home use instead of a loose jug, that difference is usually decisive.

If you're still comparing systems and brands, our overview of the best water filter lines up the options per situation. If you're wondering whether filtration adds anything at all in your home, first read our honest answer to the question of whether tap water is healthy. If you've already made up your mind, you can go straight ahead and buy a water filter.

10. Frequently asked questions

11. Conclusion

The question about faecal bacteria in tap water has a reassuring answer: 24 cases out of 565,689 measurements in a year, and if it happens you hear it from your water company and boil for three minutes. Showering, brushing teeth and washing up can carry on as normal in the meantime. A water filter plays no role in that scenario, and we don't pretend otherwise.

Where filtration does make a difference is with what's present every day in small amounts while the sources are under pressure: PFAS, lead, microplastics, medicine residues and chlorine. That's what the PureFilter Mineral+ is built for, NSF-certified under 42, 53, 61 and 372, with minerals that come back after filtering. That way you separate an incident from a daily choice, and that's exactly the nuance that usually gets lost in the news about faecal bacteria in tap water.