Water hardness in Shodoshima
35 mg/L soft
Tap water in Shodoshima is soft: 35 mg/L (2 gpg · 1.9 °dH · 3.5 °fH).
Source: Kagawa Prefectural Wide-Area Waterworks Authority (香川県広域水道企業団), tap-water quality results FY2025 (2025) · data checked 2026-10-21
Range across supply zones: 26–58 mg/L.
Shodoshima is served by the Kagawa Prefectural Wide-Area Waterworks Authority; about half of Kagawa's tap water depends on the Kagawa Canal, which carries Yoshino River water from the Sameura and Ikeda dams, with in-prefecture sources supplying the rest, and island supplies can differ from the mainland system. Hardness is reported at 34.5 mg/L CaCO₃, ranging from 26.0 to 58.0 mg/L (2025 data). Scale builds slowly at this level; a light white film on kettles and taps is possible, and a softener is rarely needed.
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 | 35 mg/L |
|---|---|
| Utility | Kagawa Prefectural Wide-Area Waterworks Authority (香川県広域水道企業団) |
How Shodoshima compares
- Tap water in Shodoshima is 31 % softer than the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 195 of 228 in Japan (1 = hardest); 15 % of these cities have softer water.
- In Kagawa it is number 13 of 16 cities; the regional median is 46 mg/L.
- Nearest city with clearly softer water: Utazu, 47 km away (28 mg/L).
- Nearest city with clearly harder water: Sanuki, 26 km away (63 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 Shodoshima
| 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 Shodoshima water hard or soft?
It is soft: 35 mg/L as CaCO₃ (2 gpg, 1.9 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Shodoshima 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 Shodoshima water?
2 gpg, equal to 1.9 °dH, 3.5 °fH or 35 mg/L calcium carbonate.
What dishwasher salt setting should I use in Shodoshima?
For 35 mg/L (1.9 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Shodoshima?
No. With soft water a softener adds nothing.
Source
Source: Kagawa Prefectural Wide-Area Waterworks Authority (香川県広域水道企業団), tap-water quality results FY2025 (2025). Method: figure published by the water supplier. Kagawa Prefectural Wide-Area Waterworks Authority (香川県広域水道企業団), tap-water quality results FY2025 · Outdated figure? Tell us