Water hardness in Okazaki
19 mg/L soft
Tap water in Okazaki is soft: 19 mg/L (1.1 gpg · 1.1 °dH · 1.9 °fH).
Source: Okazaki City Waterworks, water-quality report FY2025 (令和7年度水道水質報告書), tap points (2025) · data checked 2026-10-21
Range across supply zones: 8–31 mg/L.
Okazaki's tap water is supplied by Okazaki City Waterworks and Sewerage Bureau; the intake mix is not confirmed here, but piped water in Aichi Prefecture comes mainly from rivers and reservoirs fed by short, steep catchments. The reported figure is 19.1 mg/L CaCO₃ (range 8.1 to 30.7 mg/L, 2025 data); the spread is wide, so the value at your tap depends on where in the supply area you live. At this level scale is rarely a problem, soap lathers easily and a softener is unnecessary.
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 | 19 mg/L |
|---|---|
| Utility | Okazaki City Waterworks and Sewerage Bureau |
How Okazaki compares
- Tap water in Okazaki is 62 % softer than the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 222 of 228 in Japan (1 = hardest); 3 % of these cities have softer water.
- In Aichi it is number 6 of 8 cities; the regional median is 20 mg/L.
- Nearest city with clearly softer water: Toyota, 15 km away (11 mg/L).
- Nearest city with clearly harder water: Toyokawa, 26 km away (30 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 Okazaki
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 1 °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 Okazaki water hard or soft?
It is soft: 19 mg/L as CaCO₃ (1.1 gpg, 1.1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Okazaki 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 Okazaki water?
1.1 gpg, equal to 1.1 °dH, 1.9 °fH or 19 mg/L calcium carbonate.
What dishwasher salt setting should I use in Okazaki?
For 19 mg/L (1.1 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Okazaki?
No. With soft water a softener adds nothing.
Source
Source: Okazaki City Waterworks, water-quality report FY2025 (令和7年度水道水質報告書), tap points (2025). Method: figure published by the water supplier. Okazaki City Waterworks, water-quality report FY2025 (令和7年度水道水質報告書), tap points · Outdated figure? Tell us