Water hardness and tap water in Heiligenhaus

Kreis Mettmann, Nordrhein-Westfalen · Postcode 42579

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

• Limits of the Drinking Water OrdinancemetAll tested parameters (19), at the waterworks
• Water hardness20.4 °dH, hardNo legal limit, only a range
• Data coverageCore parameters: 7 of 7Score based on complete data

Verified drinking-water values

Note from the test report (in the German original): Durchschnitt aller Werte 2025 der Stadtwerke, keine einzelne Probe; ein Probenort steht nicht in der Tabelle. Sie nennt Tetrachlorethen mit 0,0036 mg/l, die Summe aus Tri- und Tetrachlorethen aber mit < 0,0001 mg/l (Grenzwert der Summe 0,01 mg/l). Das widerspricht sich, verbindlich sind die Stadtwerke. Die Calcitlösekapazität liegt mit 25,3 mg/l über der Anforderung 5 mg/l.

Is a value wrong or out of date?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

Background on household plumbing, not a measurement: in Heiligenhaus, 55 % of buildings with living space were built before 1970, and a further 18 % 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 Heiligenhaus

• Nitrate 6.4 mg/L – about 13 % of the limit of 50 mg/L and in the unremarkable range. Boiling does not reduce nitrate.
• PFAS (sum of PFAS-20) 3.5 ng/L – about 4 % 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 2 µg/L – within the checked range against a limit of 10 µg/L. In some regions uranium occurs naturally from the rock (geogenic).
• pH 7.46 – 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 Heiligenhaus in everyday life

At 20.4 °dH, Heiligenhaus 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 Heiligenhaus 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 Heiligenhaus 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)

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.

Against the other thresholds of Annex 6, the water would qualify as: low in sodium (“suitable for a low-sodium diet”) (Sodium 12.3 mg/l, threshold below 20 mg/l).

Questions about baby food are answered by your midwife, your paediatrician and the health office (Gesundheitsamt).

Frequently asked questions about tap water in Heiligenhaus

WaterScore

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

Data coverage: 7 of 7 core parameters. 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 v4: how we calculate the WaterScore.

Evidence: cite and check

• Trinkwasseranalyse 2025 gem. Trinkwasserverordnung, Durchschnitt aller Werte (Stadtwerke Heiligenhaus) · SHA-256 of the evaluated file: 0c4eb7d3a77603d2…, checked on 1 November 2026

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

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

Data as of: 2025 · verified: 24 of 24 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 Heiligenhaus. Retrieved from https://trinkwassermonitor.ink/en/tap-water/heiligenhaus/.”

Further information

• German version: Trinkwasser in Heiligenhaus
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