Where does our drinking water come from? Source, treatment and your region

Reading time: ~11 minutes

Two sources, three routes to your tap

The question of where our drinking water comes from therefore has no national answer but a regional one. If you live in Drenthe or Noord-Brabant, you almost certainly drink water pumped up from the ground. If you live in Rotterdam or The Hague, you drink river water that has first spent months in a storage reservoir or in the dunes. Both come out of the same tap and meet the same law, but they have made a completely different journey.

The Drinkwaterplatform (the Dutch drinking water platform) distinguishes three routes: groundwater, surface water and bank-filtered groundwater. The last is an in-between form and supplies about 5% of the total. Below we go through them one by one, followed by a table where you can look up your own water company.

Groundwater: 60% of our tap water

Groundwater is rainwater that has seeped down through layers of sand and clay over years to centuries. Along the way the soil holds back particles, bacteria and part of the contamination. The soil thus does the rough work before a water company is even involved, and that is exactly why groundwater is the preferred source: it needs less treatment.

According to the Drinkwaterplatform, the wells usually reach 40 to 300 metres deep. Vitens (a water company serving the east and centre of the country) pumps from 20 to 200 metres, Oasen from 15 to 100 metres and Brabant Water down to about 300 metres. The deeper the well, the older the water and the better it is shielded from what happens at the surface.

That protection is not a guarantee for eternity. The Drinkwaterplatform writes that groundwater has been a reliable source for more than 150 years, but that its high quality can no longer be taken for granted: new substances increasingly reach the deeper layers, and treatment becomes more expensive as a result. Which provinces are most affected shows in the regional differences in tap water quality by region.

What groundwater typically brings with it

• Minerals: along the way the water dissolves calcium and magnesium from the soil. That generally makes groundwater regions harder.
• Iron and manganese: naturally present in some layers, and the reason water companies aerate and filter.
• Stable temperature: deep groundwater hardly varies with the seasons.

If you get a metallic taste or discolouration from the tap at home, the cause usually lies not in the source but in the pipework. We cover that separately under iron in tap water.

Surface water: the Rhine, the Meuse and the IJsselmeer

The other 40% comes from open water. The main sources are the Rhine, the Meuse and the IJsselmeer, supplemented by the Lek, the Lekkanaal, the Haringvliet, the Afgedamde Maas and the Drentsche Aa. Straight after intake, that water is not fit to drink: it contains suspended material, bacteria and substances from agriculture, industry and households.

Water companies solve this in two ways. The first is the storage reservoir: Evides lets Meuse water flow through three reservoirs in a row in the Biesbosch, where settling, sunlight and time do most of the work. The second is dune infiltration, more on that below.

Surface water has a drawback and an advantage. The drawback is vulnerability: a discharge or a dry summer is immediately noticeable in the source. The advantage is that the system is already built for intensive treatment, including ozone and activated carbon, so there are more barriers in the chain by default than with a simple groundwater extraction. What ends up remaining in the water is tracked by Evides in five groups of substances, including pharmaceuticals and pesticides.

Bank filtration and dune infiltration

Bank-filtered groundwater is the in-between form. Right next to a river, groundwater is pumped up that partly originates from the river and has been filtered by the riverbank along the way. It is therefore river water with natural pre-treatment, and it supplies about 5% of Dutch drinking water.

Dune infiltration works on the same principle, but in a controlled way. Waternet (the water company for Amsterdam and surroundings) lets water from the Lekkanaal at Nieuwegein flow to the Amsterdam Water Supply Dunes, where it seeps through the sand for about 90 days. Layers of sand, sunlight, air and time remove bacteria, viruses and other harmful substances in that period. Only after that does the actual treatment in the plant begin.

PWN, Dunea and Evides use the same route in the North Holland dunes, the South Holland dunes, and at Ouddorp and Haamstede respectively. That explains why the tap water in Amsterdam and in The Hague tastes so soft: dune water picks up far less lime along the way than deep groundwater in the east and south of the country.

Which water company supplies your water?

The Netherlands has ten water companies, each with its own area and its own mix of sources. Find your region below. For seven of the companies we have an in-depth page on their water quality, sources and hardness.

If you want to know exactly for your address, the postcode check of your own water company is the quickest route. Besides the source, it usually gives the hardness too, and that value is handy if you want to know how hard the water is in your municipality.

From source to tap: what happens along the way

Between the source and your tap lies a treatment line that differs per company but roughly follows the same logic. Waternet describes nine steps for its surface water line, and they are a good example of everything that happens before the water reaches your home.

1. Removing coarse dirt: iron chloride makes fine particles clump together, after which they settle.
2. Sand and gravel filtration: beneficial bacteria break down part of the substances.
3. Natural purification: about 90 days in the dunes or around three months in a lake.
4. Second sand filtration in the treatment plant.
5. Ozone: breaks down residues of medicines and pesticides and kills bacteria.
6. Softening: lime is bound to grains that are then removed.
7. Activated carbon: removes remaining pesticides and taste and odour compounds.
8. Slow sand filtration as the final barrier.
9. Checks: several laboratory checks per day.

After that the water enters the network: according to the key figures from Vewin (the association of Dutch water companies), about 122,000 kilometres of pipe, accounting for 1,117 million cubic metres of drinking water delivered per year. Per person we use 128.1 litres a day. What that costs, you can work out in our overview of what a cubic metre of drinking water costs: according to the same Vewin figures, the sector average was €1.70 per cubic metre.

If you want to know how much of those 128.1 litres actually ends up in your glass, you will find the answer at how much water you need per day. Most of it goes to showering, the toilet and the washing machine.

Why one source says 55% and another 65%

If you research this topic, you come across different percentages. That is not sloppiness but a difference in counting, and it is useful to know which number you are looking at.

The differences therefore come down to two choices: does bank-filtered groundwater count as groundwater, and do you count the water taken in or the water delivered? In between lies the loss in treatment and in the network. All three figures are correct, as long as you state which count you are using. The easiest to remember is the RIVM ratio: about six in ten glasses of tap water begin underground.

What the source means for taste and hardness

The origin of your drinking water is not a piece of trivia but something you taste every day. Three things are directly linked to it.

Hardness

Deep groundwater dissolves calcium and magnesium along the way. As a result, the water in large parts of Brabant, Limburg and the east is harder than in the dune regions along the coast, where the water companies also actively soften it. You see that difference in your kettle and your showerhead, and we have mapped it in hard water in the Netherlands.

Taste and odour

Surface water lines use ozone and activated carbon and therefore often deliver neutral-tasting water. Even so, something can still be added in the pipe network or in your own home, from a slight chlorine taste to the taste of stagnant water in the morning. The latter has nothing to do with the source and everything to do with how long the water has stood in your own pipes.

What remains despite the treatment

Water companies treat to the standards of the Drinkwaterbesluit, and the Inspectie Leefomgeving en Transport (ILT, the Dutch Human Environment and Transport Inspectorate) checks whether they succeed. Standards are not zero values, however. For substances such as PFAS, the discussion about stricter limits is still in full swing, and what that means concretely per region you can read at PFAS measurements in the Netherlands. If you doubt whether your water is safe, the question of whether tap water is healthy is a better starting point than a search for the worst water in the country.

What a water filter does and doesn’t change

First the honest part: a water filter changes nothing about where your water comes from. Your source is fixed, your water company is fixed, and that company has already done the heavy work before the water flows into your home. A filter is not a replacement for that treatment and not an emergency measure. It is about the last stretch: what still comes out of your tap after 122,000 kilometres of pipe and after your own installation, and how it tastes.

The PureFilter Mineral+ sits on the cold water line under your sink and works with five filter layers: a pre-filter, two layers of carbon fibre, Swedish Mineral Rock™ and a post-filter. In the test at Equinox Labs, an independent laboratory, all 40 chemical substances tested were reduced in 2026, by 75% to 99.97%. For PFAS the reduction is 83% to 85%, including PFOA and PFOS. Chlorine taste and smell disappear with 99.97% less chlorine, and lead, mercury, arsenic and cadmium came out below the detection limit. In the final step, Swedish Mineral Rock™ adds calcium, magnesium and potassium.

What the filter does not do, we say just as plainly. It is not a water softener, so your kettle will not scale up any less because of it. It does not disinfect: it is made for Dutch tap water, which arrives at your home microbiologically safe already. And it changes nothing about the source itself. If you want to compare which technique tackles which substance, you will find that overview on our page about which filter type suits groundwater and which suits surface water.

At PureFilter we see that customers mainly opt for a permanent filter once they discover that their region runs on river water and they taste a hint of chlorine. That is also the group that notices the difference fastest. If you would first like an overview of the whole field, what to look for when comparing water filters will help. All the models we supply ourselves, the water filters for behind the cold water tap, run on the same principle.

Source, water company and filter: who does what

The table shows why the two questions have to be kept apart. Whether your water is safe is answered by the water company. Whether your water tastes good and what still changes on the last stretch is something you answer yourself. How that works technically is explained in our guide to how a water filter works, and the installation itself is covered step by step in the guide to connecting a water filter yourself.

Frequently asked questions

Conclusion

To the question where does drinking water come from, the answer in the Netherlands is twofold: about 60% from groundwater and 40% from surface water, extracted at some 200 locations and spread across ten water companies, each with its own area. If you live in Drenthe, you drink water from the ground. If you live in Amsterdam or The Hague, you drink river water that has spent months in the dunes.

That difference explains more than you might think: how hard your water is, why your kettle scales up faster in one province than in another, and which substances a water company has to tackle extra. Look up your own source with your water company, and you immediately know which question applies to you.

And what happens after that, on the last stretch between the meter cupboard and your glass, is up to you. That is where the difference begins between water that complies and water you like to drink. You will find more background on us and our range at purefilter.nl.