Water hardness and tap water in Flensburg

Flensburg, Schleswig-Holstein · Postcode 24937, 24939, 24941, 24943, 24944

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 (17), at the waterworks
• Water hardness8.5 °dH, mediumNo 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): Flensburg wird von zwei Wasserwerken versorgt: Ostseebad (ca. 55% des Versorgungsgebiets) und Süd (ca. 45%). Diese Daten stammen vom größeren Wasserwerk Ostseebad. Wasserwerk Süd liefert spürbar weicheres Wasser (separater Prüfbericht Nr. 25-24218-001/2, Probenahme 15.05.2025): Gesamthärte 7,2 statt 8,5 °dH, Calcium 41 statt 55 mg/l, Magnesium 6,2 statt 4,0 mg/l, Natrium 12 statt 17 mg/l, Chlorid 17 statt 24 mg/l, Sulfat 10 statt 22 mg/l, pH 7,92 statt 7,58. Da beide Netze redundant verbunden sind, kann ein Kunde je nach Lage aus beidem versorgt werden. pH und Leitfähigkeit wurden sowohl vor Ort als auch im Labor gemessen; hier wurde jeweils die Vor-Ort-Messung übernommen. Die Prüfberichte decken nur die chemisch-physikalische 'Parametergruppe B' ab – eine mikrobiologische Untersuchung (Coliforme Bakterien, E. coli) war unter den verlinkten Dokumenten nicht auffindbar und wurde daher nicht aufgenommen. Trihalomethane und Summe PFAS-20 sind rechnerische Summenwerte, bei denen alle 20 einzelnen PFAS-Kongenere bzw. alle THM-Einzelspezies unterhalb der jeweiligen Bestimmungsgrenze (0,0015 µg/l bzw. 0,0001–0,0003 mg/l) lagen, daher Summe = 0.

Is a value wrong or out of date?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 Flensburg, 53 % of buildings with living space were built before 1970, and a further 12 % 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 Flensburg

• Nitrate 0.72 mg/L – about 1 % of the limit of 50 mg/L and in the unremarkable range. Boiling does not reduce nitrate.
• PFAS (sum of PFAS-20) – not detectable in the sample evaluated. The limit of 0.1 µg/L (100 ng/L) has applied 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 – not detectable at the waterworks (limit 10 µg/L).
• pH 7.58 – 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 Flensburg in everyday life

At 8.5 °dH, Flensburg is in the hardness range “medium” (soft: below 8.4 °dH, medium: 8.4–14 °dH, hard: above 14 °dH).

• Dose detergent for the hardness range “medium”.
• As a rule of thumb, descale the kettle about every four to six weeks and the coffee machine as the manufacturer recommends.
• A limescale protection device is not a must at medium hardness; regular descaling is often enough.

Baby food and low sodium: tap water in Flensburg 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 Flensburg 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)

Against the other thresholds of Annex 6, the water would qualify as: low in sodium (“suitable for a low-sodium diet”) (Sodium 17 mg/l, threshold below 20 mg/l).

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 Flensburg

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 v3: how we calculate the WaterScore.

Evidence: cite and check

• Prüfbericht Trinkwasser – Wasserwerk Ostseebad, Parametergruppe B (Nr. 25-57421-001/1, Labor: UCL Umwelt Control Labor GmbH) (Stadtwerke Flensburg GmbH) · SHA-256 of the evaluated file: 62931dc2a7da9aeb…, checked on 3 October 2026

Suggested citation: Trinkwassermonitor (2025): Tap water in Flensburg. Values according to the water supplier’s test report, sampling date 6 November 2025; at the waterworks, not household plumbing. https://trinkwassermonitor.ink/en/tap-water/flensburg/

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

Data as of: 6 November 2025 · verified: 25 of 25 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 Flensburg. Retrieved from https://trinkwassermonitor.ink/en/tap-water/flensburg/.”

Further information

• German version: Trinkwasser in Flensburg
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