Water hardness in Isehara
50 mg/L soft
Tap water in Isehara is soft: 50 mg/L (2.9 gpg · 2.8 °dH · 5 °fH).
Source: Kanagawa Prefectural Waterworks, tap-water quality results FY2025 (2025) · data checked 2026-10-21
Range across supply zones: 36–65 mg/L.
Isehara is supplied by Kanagawa Prefectural Waterworks, which takes water from the Sagami River system (Lakes Sagami, Tsukui and Miyagase, linked by tunnels) and the Sakawa River system (Miho Dam). Hardness is reported at 50.2 mg/L CaCO₃, ranging from 36.0 to 65.0 mg/L (2025 data). Moderately soft water leaves visible deposits on kettles and taps over time, which regular descaling keeps in check.
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 | 50 mg/L |
|---|---|
| Utility | Kanagawa Prefectural Waterworks |
How Isehara compares
- Tap water in Isehara is close to the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 114 of 228 in Japan (1 = hardest); 50 % of these cities have softer water.
- In Kanagawa it is number 11 of 12 cities; the regional median is 62 mg/L.
- Nearest city with clearly softer water: Numazu, 52 km away (38 mg/L).
- Nearest city with clearly harder water: Ebina, 9 km away (64 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 Isehara
| 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 Isehara water hard or soft?
It is soft: 50 mg/L as CaCO₃ (2.9 gpg, 2.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Isehara 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 Isehara water?
2.9 gpg, equal to 2.8 °dH, 5 °fH or 50 mg/L calcium carbonate.
What dishwasher salt setting should I use in Isehara?
For 50 mg/L (2.8 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Isehara?
No. With soft water a softener adds nothing.
Source
Source: Kanagawa Prefectural Waterworks, tap-water quality results FY2025 (2025). Method: figure published by the water supplier. Kanagawa Prefectural Waterworks, tap-water quality results FY2025 · Outdated figure? Tell us