Water hardness in Nagano
50 mg/L soft
Tap water in Nagano is soft: 50 mg/L (2.9 gpg · 2.8 °dH · 5 °fH).
Source: Nagano City Waterworks Bureau, tap-water quality results FY2025 (2025) · data checked 2026-10-21
Range across supply zones: 11–150 mg/L.
Nagano combines riverbed water from the Sai River and the Odagiri Dam with groundwater, and about a quarter of its residents are served by the prefectural waterworks. The reported figure is 50.0 mg/L CaCO₃ (range 11.0 to 150.0 mg/L, 2025 data); the spread is wide, so the value at your tap depends on where in the supply area you live. Moderately soft water leaves visible deposits on kettles and taps over time, which regular descaling keeps in check.
Japanese waterworks report hardness (硬度) in mg/L CaCO₃; the standard is 300 mg/L and the target 10–100 mg/L.
Water data
| Total hardness | 50 mg/L |
|---|---|
| Utility | Nagano City Waterworks Bureau |
How Nagano compares
- Tap water in Nagano is close to the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 116 of 228 in Japan (1 = hardest); 48 % of these cities have softer water.
- Nearest city with clearly softer water: Matsumoto, 50 km away (36 mg/L).
- Nearest city with clearly harder water: Kumagaya, 122 km away (67 mg/L).
Ranking of the hardest and softest water in Japan →
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 Nagano
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 3 °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 Nagano water hard or soft?
It is soft: 50 mg/L as CaCO₃ (2.9 gpg, 2.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Nagano safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Japanese waterworks report hardness (硬度) in mg/L CaCO₃; the standard is 300 mg/L and the target 10–100 mg/L.
How many grains per gallon is Nagano water?
2.9 gpg, equal to 2.8 °dH, 5 °fH or 50 mg/L calcium carbonate.
What dishwasher salt setting should I use in Nagano?
For 50 mg/L (2.8 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Nagano?
No. With soft water a softener adds nothing.
Source
Source: Nagano City Waterworks Bureau, tap-water quality results FY2025 (2025). Method: figure published by the water supplier. Nagano City Waterworks Bureau, tap-water quality results FY2025 · Outdated figure? Tell us