Water hardness in Soka
59 mg/L soft
Tap water in Soka is soft: 59 mg/L (3.4 gpg · 3.3 °dH · 5.8 °fH).
Source: Soka City, water quality test results FY2025 (令和7年度 給水地点水質検査結果) (2025) · data checked 2026-10-21
Range across supply zones: 49–78 mg/L.
Soka sits in the part of Saitama where Tone and Arakawa river water treated by the prefecture is the main supply, with some cities adding their own wells; the exact mix for Soka is not confirmed here. The reported figure is 58.5 mg/L CaCO₃ (range 48.8 to 77.8 mg/L, 2025 data). Expect gradual white deposits on kettles, taps and showerheads; descaling now and then with citric acid is usually 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 | 59 mg/L |
|---|---|
| Utility | Soka City Waterworks (草加市上下水道部) |
How Soka compares
- Tap water in Soka is 17 % harder than the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 85 of 228 in Japan (1 = hardest); 63 % of these cities have softer water.
- In Saitama it is number 9 of 9 cities; the regional median is 67 mg/L.
- Nearest city with clearly softer water: Itakura, 47 km away (41 mg/L).
- Nearest city with clearly harder water: Urayasu, 22 km away (75 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 Soka
| 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 Soka water hard or soft?
It is soft: 59 mg/L as CaCO₃ (3.4 gpg, 3.3 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Soka 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 Soka water?
3.4 gpg, equal to 3.3 °dH, 5.8 °fH or 59 mg/L calcium carbonate.
What dishwasher salt setting should I use in Soka?
For 59 mg/L (3.3 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Soka?
No. With soft water a softener adds nothing.
Source
Source: Soka City, water quality test results FY2025 (令和7年度 給水地点水質検査結果) (2025). Method: figure published by the water supplier. Soka City, water quality test results FY2025 (令和7年度 給水地点水質検査結果) · Outdated figure? Tell us