Water hardness in Shimonoseki
36 mg/L soft
Tap water in Shimonoseki is soft: 36 mg/L (2.1 gpg · 2 °dH · 3.6 °fH).
Source: Shimonoseki City Waterworks Bureau, tap-water quality results FY2025 (5 districts) (2025) · data checked 2026-10-21
Range across supply zones: 28–110 mg/L.
Shimonoseki's tap water is supplied by Shimonoseki City Waterworks and Sewerage Bureau; the intake mix is not confirmed here, but piped water in Yamaguchi Prefecture comes mainly from rivers and reservoirs fed by short, steep catchments. The reported figure is 36.0 mg/L CaCO₃ (range 28.0 to 110.0 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 | 36 mg/L |
|---|---|
| Utility | Shimonoseki City Waterworks and Sewerage Bureau |
How Shimonoseki compares
- Tap water in Shimonoseki is 28 % softer than the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 190 of 228 in Japan (1 = hardest); 15 % of these cities have softer water.
- Nearest city with clearly softer water: Hiroshima, 148 km away (20 mg/L).
- Nearest city with clearly harder water: Oita, 101 km away (72 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 Shimonoseki
| 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 Shimonoseki water hard or soft?
It is soft: 36 mg/L as CaCO₃ (2.1 gpg, 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 Shimonoseki 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 Shimonoseki water?
2.1 gpg, equal to 2 °dH, 3.6 °fH or 36 mg/L calcium carbonate.
What dishwasher salt setting should I use in Shimonoseki?
For 36 mg/L (2 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Shimonoseki?
No. With soft water a softener adds nothing.
Source
Source: Shimonoseki City Waterworks Bureau, tap-water quality results FY2025 (5 districts) (2025). Method: figure published by the water supplier. Shimonoseki City Waterworks Bureau, tap-water quality results FY2025 (5 districts) · Outdated figure? Tell us