Water hardness in Shizuoka
74 mg/L moderately hard
Tap water in Shizuoka is moderately hard: 74 mg/L (4.3 gpg · 4.1 °dH · 7.4 °fH).
Source: Shizuoka City water quality test results FY2025 (BODIK open data, CC BY 4.0) (2025) · data checked 2026-10-21
Range across supply zones: 16–110 mg/L.
Shizuoka's supply combines riverbed water from the Abe River with many wells, while the Shimizu and Kambara districts use the Okitsu and Fuji river systems. The utility's 2025 data give 74.0 mg/L CaCO₃ within a range of 16.0 to 110.0 mg/L; the spread is wide, so the value at your tap depends on where in the supply area you live. Scale is noticeable on kettles, heaters and tap fittings, so descale more often; a softening cartridge is optional.
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 | 74 mg/L |
|---|---|
| Utility | Shizuoka City Waterworks |
How Shizuoka compares
- Tap water in Shizuoka is 47 % harder than the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 19 of 228 in Japan (1 = hardest); 92 % of these cities have softer water.
- In Shizuoka it is number 1 of 4 cities; the regional median is 46 mg/L.
- Nearest city with clearly softer water: Fuji, 34 km away (47 mg/L).
- Nearest city with clearly harder water: Hakone, 63 km away (110 mg/L).
Ranking of the hardest and softest water in Japan →
What it means at home
- Visible kettle scale every few weeks; vinegar or citric acid is enough.
- Water heater and washing machine: some long-term scale; a scale inhibitor slows it.
- Dishwasher: medium salt setting.
- Softener optional; pays off mainly with a gas boiler or tankless heater.
How much salt will you use for softening?
Optional. A scale inhibitor or a small softener protects the heater; soap savings are modest.
Descale a coffee machine or kettle about every 3 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Shizuoka
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 4 °dH |
| AEG / Electrolux | 2 |
| Beko | 1st |
| Hoover | S1 |
| LG | H1 |
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 Shizuoka water hard or soft?
It is moderately hard: 74 mg/L as CaCO₃ (4.3 gpg, 4.1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Shizuoka 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 Shizuoka water?
4.3 gpg, equal to 4.1 °dH, 7.4 °fH or 74 mg/L calcium carbonate.
What dishwasher salt setting should I use in Shizuoka?
For 74 mg/L (4.1 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Shizuoka?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Shizuoka City water quality test results FY2025 (BODIK open data, CC BY 4.0) (2025). Method: figure published by the water supplier. Shizuoka City water quality test results FY2025 (BODIK open data, CC BY 4.0) · Outdated figure? Tell us