Water hardness in Oslo
2.4 °dH soft
Tap water in Oslo is soft: 2.4 °dH (43 mg/L · 2.5 gpg · 4.3 °fH).
Source: Mattilsynet, Vannverksregisteret – drinking-water analyses (Vann- Og Avløpsetaten), NLOD 2.0 (2025) · data checked 2026-10-20
Range across supply zones: 36–53 mg/L.
Oslo's water comes mainly from Maridalsvannet, a lake north of the city, treated at the Oset plant; a smaller share comes from Elvåga via Skullerud. The reported hardness is 42.8 mg/L CaCO₃, with measurements from 35.9 to 52.7 mg/L. Scale builds up slowly, so a softener is rarely needed.
Norwegian waterworks report hardness in °dH or mg/L Ca; most supplies are very soft.
Water data
| Total hardness | 2.4 °dH |
|---|---|
| Utility | Oslo Kommune |
How Oslo compares
- Tap water in Oslo is 20 % harder than the median of the 89 cities we track in Norway (2 °dH).
- By hardness it ranks 36 of 89 in Norway (1 = hardest); 59 % of these cities have softer water.
- Nearest city with clearly softer water: Lillestrøm, 18 km away (1.4 °dH).
- Nearest city with clearly harder water: Nordre Follo, 20 km away (3 °dH).
Ranking of the hardest and softest water in Norway →
What it means at home
- Little or no limescale in kettles, water heaters or washing machines.
- Soap lathers easily; water does not dry skin or hair.
- Dishwasher: salt setting at minimum or off.
- No softener needed; a jug filter only changes taste.
How much salt will you use for softening?
No. Water this soft does not need softening.
Descale a coffee machine or kettle about every 6 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Oslo
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 2 °dH |
| AEG / Electrolux | 1 |
| Beko | 1st |
| Hoover | S0 |
| LG | H0 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Oslo water hard or soft?
It is soft: 43 mg/L as CaCO₃ (2.5 gpg, 2.4 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Oslo safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Norwegian waterworks report hardness in °dH or mg/L Ca; most supplies are very soft.
How many grains per gallon is Oslo water?
2.5 gpg, equal to 2.4 °dH, 4.3 °fH or 43 mg/L calcium carbonate.
What dishwasher salt setting should I use in Oslo?
For 43 mg/L (2.4 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Oslo?
No. With soft water a softener adds nothing.
Source
Source: Mattilsynet, Vannverksregisteret – drinking-water analyses (Vann- Og Avløpsetaten), NLOD 2.0 (2025). Method: figure published by the water supplier. Mattilsynet, Vannverksregisteret – drinking-water analyses (Vann- Og Avløpsetaten), NLOD 2.0 · Outdated figure? Tell us