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Answers to a few questions about purifying your own drinking water

Is it good to further purify your drinking water at home?

Reports appear fairly regularly in the media suggesting that drinking water is not clean and that it’s better to filter it further at home. You sometimes read or hear that tap water can cause health problems and that you can avoid these by buying a filter. In the Netherlands, however, it is certainly not the case that the drinking water is polluted or unsafe.

We have collected the answers to a few questions about purifying your own drinking water below:

Is drinking water polluted?

In the Netherlands, drinking water is made from groundwater or surface water. It is true that these sources are increasingly polluted with all kinds of substances, such as pesticides and medicines. These substances are removed during the production of drinking water. It is not always possible to remove them entirely, but the maximum concentration that remains is comparable to the concentration of a single paracetamol tablet dissolved in six Olympic swimming pools.

Drinking water companies continuously monitor their sources and drinking water. Numerous analyses are carried out every day: more than 500 different substances are checked for and, if they are present, the concentrations are also checked. The moment that a drinking-water company notices that there is an unknown substance present in a source and they do not know whether it will be possible to remove it and how, or a known substance is found in a high concentration, that water is no longer used to make drinking water.

The legal requirements that apply to drinking water in the Netherlands are extremely strict. So you can be sure that the tap water is safe. That is not to say that it necessarily has to be pure water. Drinking water naturally contains organic material and minerals and that is actually what ensures that it tastes nice.

Can the presence of low concentrations of pollutants in drinking water do any harm?

No, the concentrations really are too low for this. In total, a litre of drinking water is allowed to contain a maximum of 1 microgram of man-made (anthropogenic) substances. Most people drink around two litres per day. Imagine that there was 1 microgram of paracetamol in 1 litre of drinking water (in reality there would be 1000 times less, if there was any at all), then you would have taken a single paracetamol tablet after 685 years.

What is the situation with chlorine and fluoride, should these not be removed from the drinking water?

In many countries, the addition of chlorine is the main method of disinfecting water. In the Netherlands it is not: here the water is disinfected in other ways, such as using filtration (e.g. natural filtration through dune sand) or with UV light, which means that no (harmful) substances need to be added or are created.

There are also countries that add fluoride in order to prevent tooth decay. In the Netherlands, this has been banned for more than 40 years, as giving people medicine that they have not asked for is not permitted.

So neither chlorine nor fluoride is added (and they therefore do not need to be removed).

What about the videos in which drinking water turns completely brown?

These videos show the use of an ‘electrolyser’, through which an electric current runs. Tap water contains minerals that can conduct current. This causes one of the iron rods on the electrolyser to be partially dissolved in the water. The process produces ‘rust’ and that causes the brown sludge in the glass. So this is not something that comes from the water itself, instead it ends up in the water because the rod on the electrolyser dissolves due to the current. Other types of water may contain lower concentrations of minerals, and then won’t be able to conduct the current of the electrolyser. That’s why in drinking water the rod can dissolve, and in other types of water it cannot.

Is it good to remove lime from the water?

We call water that contains a lot of calcium hard water. High levels of hardness can cause problems with limescale. In order to prevent this, the water is already softened by the drinking-water company in many parts of the Netherlands. According to the law, softened water must still contain calcium and magnesium. Pure water is ‘aggressive’: since there is no longer anything at all in it, all kinds of substances such as metals and lime can in fact dissolve very easily in it. So it is not necessary to soften water further in most parts of the Netherlands.

Is it good to remove bacteria from the water?

You can find bacteria everywhere and what’s more they are crucial, including for humans. The vast majority of bacteria are certainly not harmful. Of course you do not want bacteria that can make you ill (pathogens) in the water. The requirements for drinking water are very strict: no more than one pathogen may be present in 1000 m3 of drinking water. It is therefore not necessary to take measures yourself to remove bacteria from the water.

Will it do any harm if I do decide to further filter my water?

It is not necessary to further filter tap water for any reason, but of course you can if you would like to. If you do, it is very important to keep the filter clean. If you don’t do this, all kinds of bacteria and so on can grow in it and this will make the quality of your water worse rather than better. Just think of rabbits’ and guinea pigs’ water bottles: these also always turn brown or green if you don’t clean them carefully.

Conclusion

Drinking water in the Netherlands must meet strict requirements and is of outstanding quality. It is clean, safe and cheap. There is no need to further filter the tap water at home. What’s more, you run the risk that the filter will become dirty, which will make the water dirtier rather than cleaner.