Water hardness in Frogn
0.6 °dH soft
Tap water in Frogn is soft: 0.6 °dH (12 mg/L · 0.7 gpg · 1.2 °fH).
Source: Mattilsynet, Vannverksregisteret – drinking-water analyses (Frogn Kommunale Vannforsyning), NLOD 2.0 (2025) · data checked 2026-10-20
Range across supply zones: 10–12 mg/L.
Frogn is supplied by its municipal waterworks, which in Norway normally takes surface water from lakes, with some towns using groundwater. Norwegian bedrock is mostly granite and gneiss, which gives soft water. The reported hardness is 11.6 mg/L CaCO₃, with measurements from 9.6 to 12.1 mg/L. Limescale is a minor issue here; a softener is unlikely to be necessary.
Norwegian waterworks report hardness in °dH or mg/L Ca; most supplies are very soft.
Water data
| Total hardness | 0.6 °dH |
|---|---|
| Utility | Frogn Kommune |
How Frogn compares
- Tap water in Frogn is 68 % softer than the median of the 89 cities we track in Norway (2 °dH).
- By hardness it ranks 76 of 89 in Norway (1 = hardest); 15 % of these cities have softer water.
- In Akershus it is number 6 of 7 cities; the regional median is 1.4 °dH.
- Nearest city with clearly harder water: Nordre Follo, 16 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 Frogn
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 1 °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 Frogn water hard or soft?
It is soft: 12 mg/L as CaCO₃ (0.7 gpg, 0.6 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Frogn 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 Frogn water?
0.7 gpg, equal to 0.6 °dH, 1.2 °fH or 12 mg/L calcium carbonate.
What dishwasher salt setting should I use in Frogn?
For 12 mg/L (0.6 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Frogn?
No. With soft water a softener adds nothing.
Source
Source: Mattilsynet, Vannverksregisteret – drinking-water analyses (Frogn Kommunale Vannforsyning), NLOD 2.0 (2025). Method: figure published by the water supplier. Mattilsynet, Vannverksregisteret – drinking-water analyses (Frogn Kommunale Vannforsyning), NLOD 2.0 · Outdated figure? Tell us