Water hardness in Twin Falls
16 gpg very hard
Tap water in Twin Falls is very hard: 16 gpg (274 mg/L · 15.4 °dH · 27.4 °fH).
Source: City of Twin Falls, Inorganic Chemical (IOC) Analysis Report 2025 (Magic Valley Labs, PWS 5420058, composite sample) (2025) · data checked 2026-10-23
Twin Falls pumps all of its water from wells in the Snake River Plain aquifer, a system of basalt and sediment layers recharged largely by irrigation canal water. Groundwater here dissolves calcium and magnesium from the volcanic and sedimentary layers, giving very hard water at 274 mg/L CaCO₃. Scale is heavy on heaters; softeners are common.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 16 gpg |
|---|---|
| Calcium (mg/L) | 58.5 |
| Magnesium (mg/L) | 27.4 |
| Utility | City of Twin Falls Water Department |
How Twin Falls compares
- Tap water in Twin Falls is 77 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 316 of 1372 in the United States (1 = hardest); 77 % of these cities have softer water.
- In Idaho it is number 2 of 9 cities; the regional median is 9.4 gpg.
Ranking of the hardest and softest water in the United States →
What it means at home
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How much salt will you use for softening?
Yes. At this hardness a softener pays for itself through appliance life and detergent.
Descale a coffee machine or kettle about every 1 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Twin Falls
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 15 °dH |
| AEG / Electrolux | 4 |
| Beko | 4th |
| Hoover | S2 |
| LG | H3 |
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 Twin Falls water hard or soft?
It is very hard: 274 mg/L as CaCO₃ (16 gpg, 15.4 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Twin Falls 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 Twin Falls water?
16 gpg, equal to 15.4 °dH, 27.4 °fH or 274 mg/L calcium carbonate.
What dishwasher salt setting should I use in Twin Falls?
For 274 mg/L (15.4 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Twin Falls?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: City of Twin Falls, Inorganic Chemical (IOC) Analysis Report 2025 (Magic Valley Labs, PWS 5420058, composite sample) (2025). Method: figure published by the water supplier. City of Twin Falls, Inorganic Chemical (IOC) Analysis Report 2025 (Magic Valley Labs, PWS 5420058, composite sample) · Outdated figure? Tell us