Water hardness in Toyohashi
48 mg/L soft
Tap water in Toyohashi is soft: 48 mg/L (2.8 gpg · 2.7 °dH · 4.8 °fH).
Source: Toyohashi City Waterworks, water-quality test results FY2025, preliminary (令和7年度水道水質試験結果 浄水 速報値), tap points (2025) · data checked 2026-10-21
Range across supply zones: 15–150 mg/L.
Toyohashi's tap water is supplied by Toyohashi 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 utility's 2025 data give 48.4 mg/L CaCO₃ within a range of 15.0 to 150.4 mg/L; the spread is wide, so the value at your tap depends on where in the supply area you live. Scale builds slowly at this level; a light white film on kettles and taps is possible, and a softener is rarely needed.
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 | 48 mg/L |
|---|---|
| Utility | Toyohashi City Waterworks and Sewerage Bureau |
How Toyohashi compares
- Tap water in Toyohashi is close to the median of the 228 cities we track in Japan (50 mg/L).
- By hardness it ranks 121 of 228 in Japan (1 = hardest); 47 % of these cities have softer water.
- In Aichi it is number 1 of 8 cities; the regional median is 20 mg/L.
- Nearest city with clearly softer water: Toyokawa, 6 km away (30 mg/L).
- Nearest city with clearly harder water: Shizuoka, 94 km away (74 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 Toyohashi
| 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 Toyohashi water hard or soft?
It is soft: 48 mg/L as CaCO₃ (2.8 gpg, 2.7 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Toyohashi 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 Toyohashi water?
2.8 gpg, equal to 2.7 °dH, 4.8 °fH or 48 mg/L calcium carbonate.
What dishwasher salt setting should I use in Toyohashi?
For 48 mg/L (2.7 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Toyohashi?
No. With soft water a softener adds nothing.
Source
Source: Toyohashi City Waterworks, water-quality test results FY2025, preliminary (令和7年度水道水質試験結果 浄水 速報値), tap points (2025). Method: figure published by the water supplier. Toyohashi City Waterworks, water-quality test results FY2025, preliminary (令和7年度水道水質試験結果 浄水 速報値), tap points · Outdated figure? Tell us