PFAS in the tap water in Sliedrecht
The tap water in Sliedrecht meets the legal standard and stays well below the RIVM advice for PFAS. That is low for South Holland. Here you can read what is in your water, what Oasen measures itself and what you can do yourself.
See the figures Shop ZeroWaterHow much PFAS is in the tap water in Sliedrecht?
- The tap water in Sliedrecht meets the legal standard.
- It is well below the RIVM advice: more than 7 times lower.
- The RIVM says: just keep drinking tap water.
What does Oasen measure itself?
Sliedrecht gets its tap water from Oasen, from the De Laak treatment plant in Lexmond. Oasen publishes the average of the past year for each treatment plant. These are the figures for De Laak, July 2025 to June 2026:
| What is measured | Value | Compared with |
|---|---|---|
| PFAS weighted by harmfulness (PFOA equivalents)* | 0.6 ng/l | RIVM advice: 4.4 ng/l |
| 20 PFAS added up (EU method)** | 6.7 ng/l | Legal limit: 100 ng/l |
| PFOA (counts most heavily) | 0.4 ng/l | PFOS, PFNA and GenX: average 0.0 |
| PFBA and PFBS (short PFAS, count for little) | 3.2 and 3.1 ng/l | Together less than 0.2 in PFOA equivalents |
| TFA (very short PFAS, measured separately) | 0.2 micrograms per litre | RIVM guideline for TFA: 2.2 micrograms per litre |
Why is the second number higher? It simply adds up 20 types of PFAS, without looking at how harmful each type is. The RIVM advice does take that into account. Even if you include TFA using the RIVM method, Sliedrecht stays at around 1 ng/l: well below the advice.
Why is it low in Sliedrecht?
Much of the drinking water in South Holland is made from river water from the Meuse or the Rhine. There, the PFAS level is often above the RIVM advice. According to Greenpeace, this applies to 81% of the people in South Holland, including neighbouring Dordrecht. Oasen works differently: it makes drinking water from riverbank groundwater. That is water from the river Lek that first seeps slowly through the soil. The soil works as a natural filter. Oasen then treats the water further, including with activated carbon. See the figures for all of South Holland.
In 2023, Oasen reported 0.5 ng/l for the Alblasserwaard region. So the level has been low and stable for several years. Not sure about your address? Look up your postcode in the Greenpeace postcode checker (in Dutch).
* Weighted by harmfulness (PFOA equivalents), using the calculation method of the RIVM (Dutch National Institute for Public Health and the Environment). Source: Oasen, PFAS report for the De Laak treatment plant (Alblasserwaard and Vijfheerenlanden region), average July 2025 to June 2026. Greenpeace does not list Sliedrecht separately; with this value, Sliedrecht falls in the lowest group of the Greenpeace analysis (0 to 2.2 ng/l).
** Sum of the 20 PFAS in the EU Drinking Water Directive. Levels may vary by measurement.
What is PFAS?
PFAS is a large group of man-made substances. They are found in many things you use every day.
- Non-stick pans
- Rain jackets and outdoor clothing
- Food packaging
- Cosmetics and firefighting foam
Why is it called a ‘forever chemical’?
- PFAS hardly break down in nature.
- They enter rivers and groundwater through factories and products.
- That water is also used to make drinking water.
- They stay in your body for a long time.
Why PFAS deserves attention
The RIVM says: together, people in the Netherlands take in more PFAS than is good for our health. This comes mainly from food, but also from drinking water.
It builds up
Your body clears PFAS only slowly. Small amounts add up over the years.
Effect on your immune system
According to the RIVM, even small amounts of PFAS can make your immune system work less well.
The advice is stricter than the law
The RIVM advises 4.4 nanograms per litre. The law is less strict. Below you can read the difference.
Law and advice: what's the difference?
There are two numbers you may read about. They don't measure exactly the same thing, but this is how it works:
- The law (EU, since 12 January 2026): a maximum of 100 nanograms per litre for 20 PFAS combined. Dutch tap water meets this standard.
- The RIVM advice: 4.4 nanograms per litre. Here the RIVM gives more weight to how harmful each type of PFAS is.
The advice is stricter because there is new knowledge about the effects of PFAS. The government is waiting for advice from the WHO before changing the law.
Good to know
- Tap water in the Netherlands is safe to drink, say the RIVM and the drinking water companies.
- Drinking water made from groundwater (mainly in the east and north) contains less PFAS.
- Drinking water made from river water (mainly in the west) contains more PFAS.
- Boiling does not remove PFAS from your water.
ZeroWater filters PFAS
Just keep drinking tap water. Want to take in less PFAS through your water? Then a certified filter is a simple extra step.
less PFAS in your water
This percentage applies to PFOA and PFOS, the two best-known and most studied PFAS. The ZeroWater 5-stage filter has been tested for these to the NSF/ANSI 53 standard and certified by the independent institute IAPMO. View the certificate.
Tested, certified
Not a promise, but an independently tested result. Tested with far more PFOA and PFOS than is found in Dutch tap water.
More than just PFAS
The filter is also certified for lead, chromium-6, mercury and chlorine. That makes your water taste purer too.
See it for yourself 000 PPM
Every jug comes with a TDS meter. It shows how pure your water is. Does it show 006? Then it's time for a new filter.
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Add to cartView product →Questions about PFAS in Sliedrecht
Can I still drink the tap water in Sliedrecht?
Yes. The tap water in Sliedrecht meets the legal standard and is well below the RIVM advice. The RIVM and Oasen advise you to keep drinking tap water. Want to take in less PFAS? Then you can filter your water as an extra step.
Does Chemours in Dordrecht affect my tap water?
The tap water in Sliedrecht comes from the De Laak treatment plant in Lexmond, some distance further along the river Lek. In the latest measurement year (July 2025 to June 2026), Oasen found an average of 0.0 ng/l of GenX there, the best-known Chemours substance. The PFAS concerns around Chemours are mainly about emissions to air, soil and vegetable gardens. For that topic, see pfasinfo.nl (in Dutch).
Does ZeroWater filter all PFAS?
The honest answer: ZeroWater is certified for PFOA and PFOS, the two best-known PFAS. There are thousands of types of PFAS. We have no certificate for the other types, so we don't make any promises about them.
Does the TDS meter show how much PFAS is in my water?
No. The meter measures dissolved solids such as limescale and metals. PFAS are present in such tiny amounts that a TDS meter can't measure them. The meter does help you see when your filter is used up: when it shows 006, replace your filter.
Does boiling or bottled water help?
Boiling does not remove PFAS from water. According to the RIVM and the drinking water companies, bottled water is not the answer, and it creates a lot of plastic waste. A filter on your regular tap water is a simpler alternative.
How often should I replace the filter?
That depends on your tap water. The harder your water, the faster the filter fills up. The water in Sliedrecht is soft (7.2 °dH according to Oasen), so your filter lasts relatively long. Test your water with the TDS meter: when it shows 006, it's time for a new filter.
Know what you drink
Just tap water, but with less PFAS. For you and your family in Sliedrecht.
Shop ZeroWater Replacement filters- RIVM (Dutch National Institute for Public Health and the Environment) – PFAS in drinking water. rivm.nl/pfas/drinkwater
- EU Drinking Water Directive 2020/2184 (PFAS standard in force since 12 January 2026). eur-lex.europa.eu
- Oasen – PFAS and drinking water sources, results per region. oasen.nl (in Dutch)
- Oasen – PFAS report, De Laak treatment plant (Alblasserwaard and Vijfheerenlanden), average July 2025 to June 2026. View PDF (in Dutch)
- Oasen – Water hardness and composition per town (Sliedrecht: De Laak treatment plant). oasen.nl (in Dutch)
- Het Kompas Sliedrecht – Future challenges for the water in Sliedrecht (Oasen, 2023). hetkompassliedrecht.nl (in Dutch)
- PFAS levels per municipality and province: analysis by Greenpeace Netherlands based on measurement data from the ten Dutch drinking water companies, September 2026. View the source (in Dutch).
- Greenpeace Netherlands – explanation and methodology of the PFAS tap water postcode checker, 22 September 2026. View PDF (in Dutch)
- Central PFAS information point South Holland South. pfasinfo.nl (in Dutch)
- ZeroWater Performance Data Sheet, IAPMO certification to NSF/ANSI 53 and 42. View PDF
ZeroWater is certified for the reduction of PFOA and PFOS. Results were achieved under laboratory conditions; actual results may vary.