Water hardness in Manno
46 mg/L soft
Tap water in Manno is soft: 46 mg/L (2.7 gpg · 2.5 °dH · 4.5 °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: 23–74 mg/L.
Manno 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. The utility's 2025 data give 45.5 mg/L CaCO₃ within a range of 23.0 to 74.0 mg/L; 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 | 46 mg/L |
|---|---|
| Utility | Kagawa Prefectural Wide-Area Waterworks Authority (香川県広域水道企業団) |
How Manno compares
- Tap water in Manno is 9 % softer than the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 133 of 228 in Japan (1 = hardest); 41 % of these cities have softer water.
- In Kagawa it is number 9 of 16 cities; the regional median is 46 mg/L.
- Nearest city with clearly softer water: Utazu, 20 km away (28 mg/L).
- Nearest city with clearly harder water: Ayagawa, 9 km away (77 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 Manno
| 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 Manno water hard or soft?
It is soft: 46 mg/L as CaCO₃ (2.7 gpg, 2.5 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Manno 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 Manno water?
2.7 gpg, equal to 2.5 °dH, 4.5 °fH or 46 mg/L calcium carbonate.
What dishwasher salt setting should I use in Manno?
For 46 mg/L (2.5 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Manno?
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