Water hardness in Kochi
39 mg/L soft
Tap water in Kochi is soft: 39 mg/L (2.3 gpg · 2.2 °dH · 3.9 °fH).
Source: Kochi City Waterworks and Sewerage Bureau (高知市上下水道局), water quality test results FY2025 (2025) · data checked 2026-10-21
Range across supply zones: 22–68 mg/L.
Kōchi draws on the Kagami, Yoshino (Kōchi diversion) and Niyodo river systems, plus wells at four sites. Hardness is reported at 38.8 mg/L CaCO₃, ranging from 22.0 to 68.0 mg/L (2025 data); the spread is wide, so the value at your tap depends on where in the supply area you live. Limescale is mild here, appearing slowly on kettles and taps, so occasional descaling is enough.
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 | 39 mg/L |
|---|---|
| Utility | Kochi City Waterworks and Sewerage Bureau (高知市上下水道局) |
How Kochi compares
- Tap water in Kochi is 23 % softer than the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 179 of 228 in Japan (1 = hardest); 21 % of these cities have softer water.
- Nearest city with clearly softer water: Tadotsu, 83 km away (21 mg/L).
- Nearest city with clearly harder water: Kotohira, 75 km away (58 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 Kochi
| 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 Kochi water hard or soft?
It is soft: 39 mg/L as CaCO₃ (2.3 gpg, 2.2 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Kochi 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 Kochi water?
2.3 gpg, equal to 2.2 °dH, 3.9 °fH or 39 mg/L calcium carbonate.
What dishwasher salt setting should I use in Kochi?
For 39 mg/L (2.2 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Kochi?
No. With soft water a softener adds nothing.
Source
Source: Kochi City Waterworks and Sewerage Bureau (高知市上下水道局), water quality test results FY2025 (2025). Method: figure published by the water supplier. Kochi City Waterworks and Sewerage Bureau (高知市上下水道局), water quality test results FY2025 · Outdated figure? Tell us