Hardest and softest tap water in Japan

All 228 cities in Japan with published data, ranked by total hardness. The national median is 50 mg/L.

Japanese waterworks report hardness (硬度) in mg/L CaCO₃; the standard is 300 mg/L and the target 10–100 mg/L.

25 cities with the hardest water

25 cities with the softest water

All cities in Japan →