Water hardness in Jōetsu
33 mg/L soft
Tap water in Jōetsu is soft: 33 mg/L (1.9 gpg · 1.8 °dH · 3.3 °fH).
Source: 上越市ガス水道局 水質検査成績年報 令和7年度 (Joetsu Gas and Water Bureau, water quality annual report FY2025) (2025) · data checked 2026-11-06
Range across supply zones: 19–53 mg/L.
9 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| mg/L | mg/L | ||
|---|---|---|---|
| 中ノ俣地区 | 29 | 29 | soft |
| 北新保地区 | 41 | 41 | soft |
| 北黒岩地区 | 35 | 35 | soft |
| 南黒岩地区 | 33 | 33 | soft |
| 小萱地区 | 33 | 33 | soft |
| 東横山地区 | 27 | 27 | soft |
| 水野地区 | 38 | 38 | soft |
| 皆口地区 | 34 | 34 | soft |
| 西ヶ窪地区 | 24 | 24 | soft |
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 | 33 mg/L |
|---|---|
| Utility | 上越市ガス水道局 Joetsu Gas and Water Bureau |
How Jōetsu compares
- Tap water in Jōetsu is 34 % softer than the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 201 of 228 in Japan (1 = hardest); 12 % of these cities have softer water.
- In Niigata it is number 2 of 3 cities; the regional median is 33 mg/L.
- Nearest city with clearly softer water: Niigata, 112 km away (19 mg/L).
- Nearest city with clearly harder water: Nagano, 56 km away (50 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 Jōetsu
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 2 °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 Jōetsu water hard or soft?
It is soft: 33 mg/L as CaCO₃ (1.9 gpg, 1.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Jōetsu 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 Jōetsu water?
1.9 gpg, equal to 1.8 °dH, 3.3 °fH or 33 mg/L calcium carbonate.
What dishwasher salt setting should I use in Jōetsu?
For 33 mg/L (1.8 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Jōetsu?
No. With soft water a softener adds nothing.
Source
Source: 上越市ガス水道局 水質検査成績年報 令和7年度 (Joetsu Gas and Water Bureau, water quality annual report FY2025) (2025). Method: figure published by the water supplier. 上越市ガス水道局 水質検査成績年報 令和7年度 (Joetsu Gas and Water Bureau, water quality annual report FY2025) · Outdated figure? Tell us