Water hardness and tap water in Duisburg

Name: Water hardness and tap water in Duisburg
Creator: Trinkwassermonitor
License: https://creativecommons.org/licenses/by/4.0/

Duisburg, Nordrhein-Westfalen · Postcode 47051, 47055, 47058, 47059, 47166

This page is a translation of the German version; the German page is authoritative. German version · Report a translation error

Short answer: The tap water in Duisburg has a total hardness of 18 °dH, hardness range “hard” (as of 2025). All tested parameters with a legal limit (7) meet the limits set by the German Drinking Water Ordinance (TrinkwV). Source: test report by Stadtwerke Duisburg. WaterScore: 100 out of 100 (data coverage: 5 of 7 core parameters).

Limits of the Drinking Water OrdinancemetAll tested parameters (7), at the waterworks
Water hardness18 °dH, hardNo legal limit, only a range
Data coverageCore parameters: 5 of 7Score based on complete data

Verified drinking-water values

Parameter	Value	Limit (TrinkwV)	Sampling date	Source	Status
Nitrate	17 mg/L 34 % of the limit	50 mg/L	2025	Stadtwerke Duisburg AG	verified
PFAS (sum)	0.012 µg/L 12 % of the limit	0.1 µg/L in force since 12 January 2026 from 12 January 2028: additionally PFAS-4 0.02 µg/L	2025	Stadtwerke Duisburg AG	verified
Lead	below the limit of quantification	0.01 mg/L from 12 January 2028: 0.005 mg/L	2025	Stadtwerke Duisburg AG	verified
Uranium	0.0006 mg/L	0.01 mg/L	2025	Stadtwerke Duisburg AG	verified
Copper	below the limit of quantification	2 mg/L	2025	Stadtwerke Duisburg AG	verified
Chloride	39 mg/L 16 % of the limit	250 mg/L	2025	Stadtwerke Duisburg AG	verified
Sulphate	70 mg/L 28 % of the limit	250 mg/L	2025	Stadtwerke Duisburg AG	verified
Sodium	22 mg/L 11 % of the limit	200 mg/L	2025	Stadtwerke Duisburg AG	verified
Calcium	110 mg/L	–	2025	Stadtwerke Duisburg AG	verified
Magnesium	11 mg/L	–	2025	Stadtwerke Duisburg AG	verified
pH	7.2	6.5–9.5	2025	Stadtwerke Duisburg AG	verified
Total hardness	18 °dH (hard)	no legal limit	2025	Stadtwerke Duisburg AG	verified
Electrical conductivity	720 µS/cm	–	2025	Stadtwerke Duisburg AG	verified

Note from the test report (in the German original): Stadtwerke Duisburg AG · Jahresmittelwert 2025 für Versorgungsbereich 1 (südlich der Ruhr einschl. Rheinhausen); Werte für das 1. Quartal 2026 lagen bei PFAS-20 21 ng/l und PFAS-4 0,5 ng/l, leicht höher als im Jahresmittel 2025. Duisburg gliedert sich in mindestens 4 Versorgungsbereiche; Bereich 4 (Baerl) misst mit 13 °dH (mittel) deutlich weicher und hat höhere PFAS-4-Werte (3,2–6,8 ng/l) als Bereich 1. Welcher Bereich eine Adresse versorgt, hängt vom Duisburger Stadtteil ab.

Is a value wrong or out of date? Report an error – we check every report against the original source.

Water at your own tap: The values describe the water the supplier delivers – not automatically the water at your tap. The water supplier is responsible up to the service connection (Hausanschluss); the building owner is responsible for the pipes beyond it. Lead can dissolve from lead pipes, leaded solder joints or old brass fittings, especially when water has stood in the pipes for a long time (stagnant water); this mainly affects buildings constructed before about 1973. If water has stood in the pipes for several hours, let it run until it comes out cool. If you suspect lead pipes, a lead analysis of the stagnant water by an accredited laboratory will help.

Background on household plumbing, not a measurement: in Duisburg, 69 % of buildings with living space were built before 1970, and a further 8 % between 1970 and 1979 (Zensus 2022, Statistisches Bundesamt, dl-de/by-2-0). (Zensus 2022) According to the German Environment Agency (Umweltbundesamt), lead pipes exist at most in houses built before 1973 – and by no means in all of them. Whether there are any in your house is known to the owner or a plumber. (UBA)

What the values mean for Duisburg

Nitrate 17 mg/L – about 34 % of the limit of 50 mg/L and in the medium range – such values occur in catchments shaped by agriculture. Boiling does not reduce nitrate.
PFAS (sum of PFAS-20) 12 ng/L – about 12 % of the limit of 100 ng/L (since 12 January 2026).
Lead – not detectable at the waterworks. Lead gets into the water almost only through old lead pipes in household plumbing, not via the supplier.
Uranium 0.6 µg/L – unremarkable against a limit of 10 µg/L. In some regions uranium occurs naturally from the rock (geogenic).
pH 7.2 – within the range of the Drinking Water Ordinance (6.5 to 9.5). The pH determines how corrosive the water is in household plumbing.

Water hardness in Duisburg in everyday life

At 18 °dH, Duisburg is in the hardness range “hard” (soft: below 8.4 °dH, medium: 8.4–14 °dH, hard: above 14 °dH).

Dose detergent for the hardness range “hard” – a larger amount is needed; a water softener for the washing machine can save detergent.
Limescale builds up quickly: descale the kettle about every two to three weeks, and taps and shower heads too.
In your own house, limescale protection or a water softener can be worthwhile at this hardness; in a rented flat, the owner decides.

Baby food and low sodium: tap water in Duisburg next to the bottled-water thresholds

Bottled water may only be labelled “suitable for preparing infant food” („geeignet für die Zubereitung von Säuglingsnahrung“) if it keeps to the maximum levels of the German Mineral and Table Water Ordinance (Mineral- und Tafelwasser-Verordnung, Annex 6). Here the published values for Duisburg are shown next to them, each substance on its own. This is a comparison with labelling thresholds for bottled water, not a statement on whether your tap water is suitable for baby food. (Min/TafelWV, Anlage 6)

Values at the waterworks next to the maximum levels for bottled water “suitable for infant food”
Substance	Maximum level	Value in Duisburg
Sodium	20 mg/l	22 mg/l – above
Nitrate	10 mg/l	17 mg/l – above
Nitrite	0.02 mg/l	not in the report
Sulphate	240 mg/l	70 mg/l – not above
Fluoride	0.7 mg/l	not in the report
Manganese	0.05 mg/l	not in the report
Arsenic	0.005 mg/l	not in the report
Uranium	0.002 mg/l	0.0006 mg/l – not above

For context: the German Environment Agency (Umweltbundesamt) considers preparing baby food with bottled water carrying this label necessary only in rare cases, for example when tap water is temporarily allowed to contain more than 50 mg/l nitrate. (UBA 2016, p. 59) Water from lead pipes in the house is always unsuitable for infants. (UBA 2020, p. 16) The values apply at the waterworks. Questions about baby food are answered by your midwife, your paediatrician and the health office (Gesundheitsamt).

Frequently asked questions about tap water in Duisburg

Can you drink the tap water in Duisburg?

According to the verified values, yes: All tested parameters with a legal limit (7) meet the limits set by the German Drinking Water Ordinance (TrinkwV). WaterScore: 100 out of 100 (data coverage: 5 of 7 core parameters). This applies to the water from the waterworks – restrictions can only arise from old household plumbing.

How hard is the water in Duisburg?

The total hardness is 18 °dH – hardness range “hard”. Dose detergent for the hardness range “hard” – a larger amount is needed; a water softener for the washing machine can save detergent.

Is there PFAS in the tap water in Duisburg?

Yes, in measurable amounts: according to the published analysis by Stadtwerke Duisburg (as of 2025), the sum of PFAS-20 is 0.012 (middle of the range given by the supplier) µg/l – that is 12 % of the limit of 0.1 µg/l, which has applied since 12 January 2026.

Do I need to filter my tap water in Duisburg?

Based on the verified supplier values, a filter is not necessary. It can make sense if you do not like the taste. If you suspect lead pipes in an old building, a filter does not help; a laboratory analysis at the tap does – that is a question of the household plumbing, not of the water leaving the works.

WaterScore

Total100 / 100
Chemical safety100 / 100
Heavy metals100 / 100
PFAS100 / 100
Nutrients100 / 100
General parameters100 / 100
Data timeliness100 / 100
Data quality100 / 100

Data coverage: 5 of 7 core parameters. Not in the test report: Nitrite and Arsenic. Missing parameters are neither estimated nor counted as harmless: the score is based only on the values available. It is not a health assessment and says nothing about the water beyond the service connection. Methodology v3: how we calculate the WaterScore.

Evidence: cite and check

Chemisch-physikalische Wasseranalyse Duisburg, Versorgungsbereich 1 (südlich der Ruhr einschl. Rheinhausen), Jahresmittelwert 2025 (Stadtwerke Duisburg AG) · SHA-256 of the evaluated file: f73693c03a579eee…, checked on 3 October 2026

Suggested citation: Trinkwassermonitor (2025): Tap water in Duisburg. Values according to the water supplier’s test report, sampling date 2025; at the waterworks, not household plumbing. https://trinkwassermonitor.ink/en/tap-water/duisburg/

JSON: /api/v1/evidence?city=duisburg

Data as of: 2025 · verified: 13 of 13 evaluated parameters.

This page shows only verified test data with sources, or states explicitly where data is missing (no estimated values). Cite as: “Trinkwassermonitor (2026). Tap water in Duisburg. Retrieved from https://trinkwassermonitor.ink/en/tap-water/duisburg/.”