Water hardness in Lewiston
2.1 gpg soft
Tap water in Lewiston is soft: 2.1 gpg (36 mg/L · 2 °dH · 3.6 °fH).
Source: Idaho Drinking Water Watch, chemical sample results, system ID2350015 (2025-07) · data checked 2026-10-19
Range across supply zones: 18–82 mg/L.
The figure is for the Lewiston Orchards Irrigation District, which supplies one part of Lewiston, from Idaho's Drinking Water Watch portal. It rests on 4 samples from 2025: a median of 35.7 mg/L as CaCO3 (2.1 gpg), with a range of 17.8 to 82 mg/L. Other parts of the city may differ. For this district the water is soft.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 2.1 gpg |
|---|---|
| Utility | Lewiston Orchards Irrigation Dist |
How Lewiston compares
- Tap water in Lewiston is 77 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 1256 of 1372 in the United States (1 = hardest); 8 % of these cities have softer water.
- In Idaho it is number 9 of 9 cities; the regional median is 9.4 gpg.
- Nearest city with clearly harder water: Coeur d'Alene, 144 km away (8.2 gpg).
Ranking of the hardest and softest water in the United States →
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 Lewiston
| 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 Lewiston water hard or soft?
It is soft: 36 mg/L as CaCO₃ (2.1 gpg, 2 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Lewiston safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
How many grains per gallon is Lewiston water?
2.1 gpg, equal to 2 °dH, 3.6 °fH or 36 mg/L calcium carbonate.
What dishwasher salt setting should I use in Lewiston?
For 36 mg/L (2 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Lewiston?
No. With soft water a softener adds nothing.
Source
Source: Idaho Drinking Water Watch, chemical sample results, system ID2350015 (2025-07). Method: own measurement. Idaho Drinking Water Watch, chemical sample results, system ID2350015 · Outdated figure? Tell us