Why there might soon be a little less calcium in Copenhagen’s tap water

Denmark has lagged behind its neighbours in addressing high concentrations of calcium—kalk in Danish—in its tap water, leaving residents to filter and scrape limescale on their end of the pipe.

But Hofor, the company that provides drinking water for all of Copenhagen and several of its surrounding municipalities, has finally released a schedule for rolling out centralised filtration.

Currently, Copenhagen’s city water ranks 17-25°dH on the water hardness scale, according to Hofor.

For reference, the US Geological Survey’s classifications are as follows: 0-3.37 °dH is soft, 3.38-6.7°dH is moderately hard, 6.75-10.11°dH is hard and anything over 10.12 °dH is very hard.

Hofor’s plan is to soften all water it supplies to Copenhagen residents by 2028, the company says.

The first neighbourhoods to experience a noticeable change will be Nordvest, Indre By, Østerbro, and Herlev as their water drops to 12-16 °dH this fall. These regions are primarily serviced by the Søndersø waterworks in Værløse, the site of Hofor’s new softening plant.

Valby, Vanløse, Brønshøj and Nørrebro will also see a difference this year, to the tune of 16-20 °dH—it’s less of a jump for these neighbourhoods since Søndersø provides a smaller percentage of their water. Vesterbro, Sydavnen and Amager will have to wait until at least 2024, according to Hofor’s schedule.

What will change?

The taste of a cup of Copenhagen vand (water) won’t change, but what should residents expect from softer water?

‘Hard’ water is hard on hair and skin, so you may feel both more supple and less dry after showers. Residents of Brøndby, where Hofor tested its first softening operation on a smaller scale, reduced their use of detergent by about a third and found cleaning easier and less time-consuming, Danish newspaper Politiken reports.

While most Copenhagen residents will likely be pleased with the shift, a surprising demographic is sounding alarm bells—dentists. Tandlægebladet, a trade magazine for Danish dentists, wrote that plans to soften water could lead to more cavities for Copenhageners. The magazine pointed to a 2004 study of 52,000 Danish 15-year-olds and found significantly fewer cavities in municipalities with harder drinking water, the article said.

What if it’s still too hard?

If you’re not satisfied with Hofor’s target water hardness for your area, there are commercially available systems to filter your home’s entire water supply—though they cost a pretty penny.

A more budget-friendly option is a shower filter, which should at least reduce hard water symptoms like lifeless hair and dandruff.

In January, a group of presumably itchy Copenhagen residents pitched in on a bulk order of shower filters from Germany, ordering over 200 filters direct from the manufacturer according to a post in the 59,000-member Facebook group “Expats in Copenhagen” by the group’s organiser.

Others swear by applying apple cider vinegar on the scalp after a shower.