How do we make clean tap water?

You open your tap and clear, clean water comes out. But how do we actually make that water? And where does it come from? We’ll show you step by step how we make your tap water clean and healthy, from source to tap.

Where does your water come from?

Waternet produces drinking water from two sources: river water from the Lekkanaal near Nieuwegein, and water that rises naturally in the Bethunepolder near Maarssen. This water is not yet clean enough to drink. It may contain bacteria, viruses, and other substances that can make you sick. That’s why we clean the water in 10 smart steps — with help from nature and modern technology. This way, we make sure clean drinking water comes out of your tap every single day.

Step 1: Removing the coarse dirt

The water from the Lekkanaal and the Bethunepolder contains small particles that float around because they are so light. We add iron chloride to the water, which makes these tiny particles stick together into larger flakes. These heavier flakes sink to the bottom of large tanks. What remains is already much clearer water — the first step towards clean tap water!

Step 2: Filtering with sand and gravel

Next, the water flows through a sand filter. It passes through thick layers of coarse sand and gravel. Here, the last bits of dirt still in the water are trapped. Helpful bacteria also live in this sand filter — they break down certain substances naturally. This makes the water even cleaner.

Step 3: Letting nature do its work

This is where nature takes over!

Does the water come from the Lekkanaal? Then it flows to the Amsterdam Water Supply Dunes near Vogelenzang. There, it slowly sinks into the ground. During this 90-day journey, bacteria, viruses, and other unwanted substances are removed by layers of sand — with help from sun, air, and time.
Does the water come from the Bethunepolder? Then it flows to the Waterleidingplas near Loenderveen, where it stays for about three months. Wind and sunlight keep the water moving and help clean it naturally. Many harmful substances break down on their own.

No matter which route it takes: nature cleans the water thoroughly and reliably.

Step 4: Filtering once more

After natural purification, the water enters our treatment facility. There we filter it again, this time with very fine sand. Even extremely small particles — like tiny algae or dust — get trapped. What remains is almost crystal-clear water.

Step 5: Adding ozone

In this step, we add ozone — a special gas made from oxygen. Ozone breaks down tiny leftovers, such as traces of medicines or pesticides. It also removes bacteria. The result? Fresher, safer water that tastes better too.

Step 6: Removing lime

The water still contains lime (calcium). This doesn’t harm your health, but it does leave limescale on taps and in kettles. That’s why we soften the water. We add a liquid that makes the calcium stick to small limestone pellets. We remove those pellets afterwards. This reduces the amount of calcium in the water — good for your appliances and for your skin. But we don’t remove all of it; tap water should contain some calcium.

Step 7: Activated carbon

Now the water flows through activated carbon — black granules full of tiny pores. These pores trap the last remains of pesticides or taste- and smell-causing substances. Helpful bacteria on the carbon break down these substances even further. This makes the water extra clean and pleasant to drink.

Step 8: One final filter

We filter the water one more time with very fine sand. This last step removes any remaining dirt or bacteria. After this, the water is completely clean and ready for use.

Step 9: Quality tests

We check the drinking water several times a day. In our laboratory we examine whether it meets all the required standards. If something is not right, we act immediately. This way, we keep the quality of our tap water consistently high.

Ready to drink

The clean drinking water travels through underground pipes to homes, schools, and businesses. Whether you pour a glass of water, take a shower, or water your plants — you always get reliable, high-quality tap water.

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