Water hardness in Bielefeld
The utility publishes no single figure for Bielefeld. Depending on which waterworks supplies the street, hardness runs between 4.3 and 17.1 °dH.
How hardness is classified
There is no European classification; each country sets its own bands. Here is how the country itself classifies it, and how the international scale compares:
How Germany classifies it
Internationally, from the WHO and the US Geological Survey
Does the figure apply at your address?
Not necessarily. The published figures for this city run from 4.3 °dH to 17.1 °dH, depending on the waterworks, the zone, or simply when the sample was taken. Which of them reaches a given address is a question only the utility can answer.
eleven waterworks from 4.3 dH at the softest to 17.1 dH at the hardest; the utility lists each with its figure
The figure for your address or postcode is available directly from Stadtwerke Bielefeld — and it is often printed on the water bill too.
A hardness test strip from a chemist or hardware shop costs a few euros and settles it in a minute. That is also the only way to know what comes out of your own tap rather than what leaves the waterworks.
Setting an appliance
A dishwasher, washing machine or coffee machine that asks for a level from 1 to 4 wants 1–3 here, depending on the zone.
That four-level scale is the one German detergent law used until 2007. The law moved to the three bands above; the dials did not.
The same figure on other scales
4.3–17.1 °dH · 7.7–30.5 °f · 0.77–3.05 mmol/l · 77–305 mg/L
Dishwashers and washing machines ask for hardness in different units depending on where they were sold: millimoles per litre in Germany, degrees in Austria and Switzerland, parts per million in Britain. It is one quantity read on four scales.
Where a range is given, the safe setting for an appliance is the upper end: too much softening salt does no harm, too little leaves scale.
What it means day to day
How much limescale you get depends on which waterworks supplies your street.
Hard water is not a fault
Hardness is not a safety question. Hard water is fine to drink; it just leaves more limescale.
The calcium and magnesium that make water hard are the same minerals a diet needs, and drinking water counts towards the daily intake of both. The WHO reviewed how much in Calcium and magnesium in drinking-water.
A thin carbonate layer on the inside of a pipe also protects the metal underneath from corroding. Water softened to nothing is harder on plumbing, not easier.
The water is fine to drink either way: Is the tap water in Bielefeld safe to drink?
Where the figure comes from
Published by Stadtwerke Bielefeld, which gives no measurement date.
The figure is total hardness, which counts every calcium and magnesium compound in the water. Some utilities also publish carbonate hardness, the part bound to carbonic acid, which is the share that forms limescale when the water is heated.