Water hardness in Trondheim
3.5 °dH moderately hard
Tap water in Trondheim is moderately hard: 3.5 °dH (63 mg/L · 3.7 gpg · 6.3 °fH).
Source: Mattilsynet, Vannverksregisteret – drinking-water analyses (Trondheim Vannverk), NLOD 2.0 (2023) · data checked 2026-10-20
Trondheim 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 62.7 mg/L CaCO₃. This figure dates from 2023 and may have changed. Limescale appears gradually on taps and heating elements; occasional descaling keeps it in check.
Norwegian waterworks report hardness in °dH or mg/L Ca; most supplies are very soft.
Water data
| Total hardness | 3.5 °dH |
|---|---|
| Utility | Trondheim Kommune |
How Trondheim compares
- Tap water in Trondheim is 76 % harder than the median of the 89 cities we track in Norway (2 °dH).
- By hardness it ranks 11 of 89 in Norway (1 = hardest); 89 % of these cities have softer water.
- In Trøndelag it is number 4 of 21 cities; the regional median is 1.8 °dH.
- Nearest city with clearly softer water: Stjørdal, 26 km away (1.8 °dH).
- Nearest city with clearly harder water: Midtre Gauldal, 44 km away (4.9 °dH).
Ranking of the hardest and softest water in Norway →
What it means at home
- Visible kettle scale every few weeks; vinegar or citric acid is enough.
- Water heater and washing machine: some long-term scale; a scale inhibitor slows it.
- Dishwasher: medium salt setting.
- Softener optional; pays off mainly with a gas boiler or tankless heater.
How much salt will you use for softening?
Optional. A scale inhibitor or a small softener protects the heater; soap savings are modest.
Descale a coffee machine or kettle about every 3 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Trondheim
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 4 °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 Trondheim water hard or soft?
It is moderately hard: 63 mg/L as CaCO₃ (3.7 gpg, 3.5 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Trondheim 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 Trondheim water?
3.7 gpg, equal to 3.5 °dH, 6.3 °fH or 63 mg/L calcium carbonate.
What dishwasher salt setting should I use in Trondheim?
For 63 mg/L (3.5 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Trondheim?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Mattilsynet, Vannverksregisteret – drinking-water analyses (Trondheim Vannverk), NLOD 2.0 (2023). Method: computed from supplier's calcium and magnesium. Mattilsynet, Vannverksregisteret – drinking-water analyses (Trondheim Vannverk), NLOD 2.0 · Outdated figure? Tell us