Water hardness per municipality: how hard is your water?

Published on July 11, 2026 | Reading time: ~11 minutes

How hard is your tap water actually? The answer depends entirely on where you live. The water hardness per municipality in the Netherlands ranges from approximately 4 to over 14 °dH, more than a threefold increase between the softest and hardest regions. This explains why some people hardly see any limescale in their kettle while others descale every month.

In this guide, we explain how to find out the water hardness in your municipality, which provinces have soft or hard water, why it varies, and what you can do about it. At PureFilter, we find that customers primarily want to know if their water is safe and tastes good, regardless of its hardness.

1. What is water hardness and how is it measured?

Water companies sometimes also measure hardness in millimoles per liter (mmol/l), but for consumers, the German degree is the most convenient. For comparison: besides the German degree, there is also the French degree (°fH), where 1 °fH is equal to 0.56 °dH. Dutch drinking water companies almost always report in °dH.

Hardness is generally divided into five categories. This scale helps you determine whether your municipality has soft or hard water:

The average water hardness in the Netherlands is around 8 °dH, precisely on the border between soft and medium-hard. However, this average says little about your specific municipality.

2. How to find out the water hardness in your municipality?

The most reliable source for water hardness per municipality is your own drinking water company. The Netherlands has ten regional drinking water companies, each responsible for a fixed supply area. On their website, you can enter your postcode and immediately see the current hardness of your tap water.

First, find out which company supplies your water. These are the ten Dutch drinking water companies and their main service areas:

• Vitens: Friesland, Overijssel, Gelderland, Flevoland, Utrecht, and Drenthe (the largest company, over 5.8 million customers).
• PWN: province of Noord-Holland (outside Amsterdam).
• Waternet: Amsterdam and surroundings.
• Dunea: southern part of Zuid-Holland, including The Hague and Leiden.
• Evides: southwestern Zuid-Holland, Zeeland, and Brabantse Wal, including Rotterdam.
• Oasen: eastern part of Zuid-Holland (Gouda, Alphen).
• Brabant Water: almost all of Noord-Brabant.
• WML: province of Limburg.
• WMD: province of Drenthe.
• Waterbedrijf Groningen: province of Groningen.

Do you want to be absolutely sure? Then measure the hardness yourself with a test strip. Hold the strip in the water for a few seconds and compare the color after one minute with the accompanying scale. This way, you will know the exact hardness at your tap, including any influence from your own pipes.

3. Water hardness by province and region

The table below provides an indication of water hardness per province. Please note: within one province, hardness can vary by municipality because water companies use multiple sources. Use this as a guideline and check your exact figure with your water company.

Large cities usually fall into the medium-hard category. Waternet in Amsterdam deliberately supplies softened water around 8 °dH, while cities like Maastricht and parts of Twente tend towards the hard water category. If you live in Friesland or Flevoland, you almost always have soft water and hardly any problems with limescale.

4. Why does water hardness vary by municipality?

The hardness of tap water is determined by the source from which the water company draws. There are three factors that explain the difference per municipality:

• Groundwater versus surface water: Groundwater seeps through calcareous soil layers, absorbing calcium and magnesium. Municipalities that rely on deep groundwater often have harder water than municipalities that use dune or surface water.
• Soil composition: In sandy and peat areas like Friesland and Flevoland, the soil is low in calcium, resulting in soft water. In areas with limestone or marl, such as South Limburg, the water is naturally harder.
• Central softening: Many water companies already soften the water centrally during purification to better manage limescale. The legal minimum for softening is 5.6 °dH; below that value, water becomes too aggressive for pipes. Where and how much is softened varies by company and therefore by municipality.

Because a single water company sometimes combines multiple production sites, even within the same municipality, there can be a small difference in hardness between two neighborhoods. This is another reason to use your postcode instead of just the municipality name.

5. Is hard water in your municipality harmful?

No, hard water is not harmful to your health. Milieu Centraal and RIVM confirm that the calcium and magnesium in tap water are useful minerals that contribute to your daily intake. Dutch tap water is among the cleanest in the world and meets strict legal standards, regardless of the hardness in your municipality.

The disadvantages of hard water are not in your body, but in your home. From approximately 8 to 10 °dH, you will notice the consequences:

• Limescale: white deposits on taps, in the shower, and on glassware.
• Shorter appliance lifespan: kettles, coffee makers, and washing machines clog up and last up to 30% less long.
• More soap and detergent: hard water lathers less effectively, so you use 25 to 30% more product.
• Higher energy consumption: a layer of limescale a few millimeters thick on a heating element can noticeably increase energy consumption.

Important to know: a water filter like the PureFilter does not soften hard water. Limescale throughout your home can be addressed with a water softener. A drinking water filter focuses on something different, namely the purity and taste of the water you drink. Read more about this in our guide best water filter.

6. What can you do about hard water?

Depending on what you want to achieve, tackling limescale or better-tasting drinking water, there are different solutions. It is important to know the distinction, as they do not do the same thing.

Water softener (for limescale throughout the house)

A salt-based water softener exchanges calcium and magnesium for sodium through ion exchange. It connects to the main water line and softens all water in the house. This is the best choice if you live in a municipality with hard water (12 °dH or more) and want less limescale everywhere. A softener typically costs 800 to 2,500 euros plus installation and salt.

Inline water filter (for pure drinking water)

An inline water filter such as the PureFilter Mineral+ connects under your sink and purifies the water you drink and cook with. It removes over 100 contaminants and maintains calcium, magnesium, and potassium levels using Swedish Mineral Rock™ technology. This is the choice for anyone who wants fresh, pure drinking water, in any municipality and regardless of hardness. Installation takes 5 to 10 minutes.

Filter jug (entry-level solution)

A filter jug like Brita temporarily softens the water in the jug and slightly improves the taste. Its capacity is limited to approximately 150 to 200 liters per cartridge, after which you need to replace it. Handy for on the go, but not a structural solution for hard water or thorough purification.

7. Points of attention when tackling hard water

Before choosing a solution based on the water hardness in your municipality, consider the following:

• Don't soften too much: Water below 5.6 °dH is not legally permitted and can damage pipes. A good softener maintains a healthy residual hardness.
• Retain minerals: Completely limescale-free water lacks calcium and magnesium and tastes flat. The PureFilter Mineral+ actually adds these minerals, so your water retains its fresh taste.
• Replace the filter in time: A saturated filter no longer works optimally. Replace the PureFilter cartridge every 12 months or after 15,000 to 20,000 liters. Replacement filters are available from 49.90 euros.
• Choose the right device for your purpose: Do you want less limescale in the bathroom? Then a water softener makes sense. Do you primarily want clean, tasty drinking water? Then an inline filter is sufficient, even in a municipality with hard water.

8. Comparison table: water softener, filter jug or inline filter

The choice depends on your goal. For limescale in the entire house, a water softener is the right investment. For clean and tasty drinking water in any municipality, while retaining healthy minerals, the PureFilter Mineral+ is the simplest and most affordable solution. You can read more about this distinction in our comparison under-sink water filter.

9. PureFilter Mineral+: fresh drinking water in every municipality

Whether you live in soft Friesland or harder Limburg, the PureFilter Mineral+ ensures pure, tasty drinking water everywhere. The filter removes more than 100 contaminants, including PFAS, microplastics, lead, chlorine and medicine residues, and is certified to NSF 42, 53, 61 and 372.

The special feature is the Swedish Mineral Rock™ technology. While aggressive systems such as reverse osmosis also remove beneficial minerals, the PureFilter actually adds calcium, magnesium and potassium. This way you drink water that is clean and fresh-tasting, without the flat taste of demineralized water.

At PureFilter, we see that customers in municipalities with medium to hard water often opt for the combination: an inline filter for drinking water and optionally a water softener for the bathroom. For most households that primarily want to drink fresh tap water, the filter alone is sufficient.

10. Frequently asked questions about water hardness per municipality

11. Conclusion

Water hardness varies significantly across municipalities in the Netherlands, from soft water in Friesland and Flevoland to hard water in parts of Overijssel, North Brabant and Limburg. The best way to find your exact hardness is to use the postcode tool of your drinking water company, or measure it yourself with a test strip.

Hard water is not unhealthy, but it causes limescale. If you want less limescale throughout the house, a water softener is the solution. If you primarily want clean and fresh drinking water, regardless of the hardness in your municipality, the PureFilter Mineral+ is the easiest choice. Certified to NSF 42, 53, 61 and 372, removes more than 100 contaminants and retains healthy minerals via Swedish Mineral Rock™, installed in 5 to 10 minutes.

Want to know more? Visit purefilter.nl or read our comprehensive guide on hard water in the Netherlands.