Water hardness in Kofu
18 mg/L soft
Tap water in Kofu is soft: 18 mg/L (1 gpg · 1 °dH · 1.8 °fH).
Source: Kofu City Waterworks Bureau, water quality test results FY2025 (4 rounds) (2025) · data checked 2026-10-21
Range across supply zones: 16–74 mg/L.
Kofu's tap water is supplied by Kofu City Waterworks Bureau; the intake mix is not confirmed here, but piped water in Yamanashi Prefecture comes mainly from rivers and reservoirs fed by short, steep catchments. Hardness is reported at 17.6 mg/L CaCO₃, ranging from 16.0 to 74.0 mg/L (2025 data); the spread is wide, so the value at your tap depends on where in the supply area you live. Water this soft rarely leaves scale, so kettles and showerheads stay mostly clear and a softener adds little.
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 | 18 mg/L |
|---|---|
| Utility | Kofu City Waterworks Bureau |
How Kofu compares
- Tap water in Kofu is 65 % softer than the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 225 of 228 in Japan (1 = hardest); 1 % of these cities have softer water.
- Nearest city with clearly softer water: Toyota, 144 km away (11 mg/L).
- Nearest city with clearly harder water: Okutama, 47 km away (34 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 Kofu
| 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 Kofu water hard or soft?
It is soft: 18 mg/L as CaCO₃ (1 gpg, 1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Kofu 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 Kofu water?
1 gpg, equal to 1 °dH, 1.8 °fH or 18 mg/L calcium carbonate.
What dishwasher salt setting should I use in Kofu?
For 18 mg/L (1 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Kofu?
No. With soft water a softener adds nothing.
Source
Source: Kofu City Waterworks Bureau, water quality test results FY2025 (4 rounds) (2025). Method: figure published by the water supplier. Kofu City Waterworks Bureau, water quality test results FY2025 (4 rounds) · Outdated figure? Tell us