How does Spearfish's water compare to the national average?

The USA national average is 151 mg/L. Spearfish (≈ 180+ mg/L) is 189 mg/L harder than average.

Spearfish Water Hardness & Quality Report (2026)

Water Hardness

very hard

180+ mg/L

Very Hard

estimated · not lab-verified

Source

groundwater

pH Level

8.2

neutral = 7.0

Lead

0.002 mg/L

✓ Below action level

TDS

340.9 mg/L

Est. Daily Cost

$0.91

energy & soap waste

Source: See methodology section below · Updated 2026

very hard180+ mg/LVery Hard · est.

0–60

mg/L

Soft

61–120

mg/L

Moderately Hard

121–180

mg/L

Hard

180+

mg/L

Very Hard

Appliance Damage Report

In Spearfish, your appliances are currently losing 45% efficiency due to mineral buildup.

Appliance	In Spearfish	Soft Water City	Efficiency Loss
Kettle	4.7 yrs	8.5 yrs	-45%
Washing Machine	6.6 yrs	12 yrs	-45%
Water Heater	8.3 yrs	15 yrs	-45%

Regional Water Comparison

How Spearfish compares to its nearest neighbours

City	Hardness	PFAS (ppt)	Risk	Source
▶ Spearfish, South Dakota	≈ 180+ mg/L	0 ppt	🔴 Very Hard	groundwater
Rapid City, South Dakota	≈ 180+ mg/L	9.7 ppt	🔴 Very Hard	reservoir
Gillette, Wyoming	≈ 0–60 mg/L	0 ppt	🟢 Soft	groundwater
Dickinson, North Dakota	≈ 120–179 mg/L	0 ppt	🟠 Hard	reservoir
Scottsbluff, Nebraska	≈ 180+ mg/L	0 ppt	🔴 Very Hard	groundwater

National Benchmark

How Spearfish compares to the USA average

Benchmark	Hardness	Appliance Risk
▶ Spearfish	≈ 180+ mg/L	🔴 High
USA National Avg	151 mg/L	🟠 Moderate
Scarsdale Top Rated	0.02 mg/L	🟢 None

Bring Scarsdale-quality water to your Spearfish home

Shop water softeners on Amazon.com →

Shop Now

What Makes Spearfish's Water Unique?

Local geology and source profile

Source: GroundwaterTDS: 340.9 mg/LpH: 8.2

The City of Spearfish Public Water System supplies Spearfish and North Spearfish in Lawrence County, South Dakota. Its water originates from local groundwater wells drawing from the Black Hills area. While specific reservoirs or rivers aren't named as primary sources, the Black Hills watershed acts as the recharge zone for these aquifers. Precipitation and snowmelt seep into the fractured limestone terrain, replenishing the supply. Treatment is handled at the city's water treatment facilities, with operational contacts available at 605-642-1333 or 605-717-1170.

The groundwater travels through Paleozoic and Mesozoic sedimentary rock formations. Key among these are the Madison Limestone (dating to the Mississippian period) and the Minnelusa Formation (from the Permian age). These layers, particularly the Madison Aquifer and Minnelusa Formation, are rich in calcium and magnesium. As water leaches these minerals from the carbonate rocks, it results in a very hard water supply, a characteristic amplified by the region's karst geology.

This very hard water can lead to significant scale buildup in pipes, water heaters, dishwashers, and washing machines, ultimately reducing their efficiency and lifespan. You might notice white deposits on kettles and fixtures, and laundry may feel stiff without the use of a water softener. Homeowners can mitigate these effects through regular descaling with vinegar, annual flushing of water heaters, and using low-flow aerators. For most households, installing a water softener is highly recommended to combat scaling and improve how effectively soap lathers.

Geology & Source: Paleozoic and Mesozoic sedimentary rocks; limestone and dolomite formations like Madison Aquifer and Minnelusa Formation create very hard water.

Other South Dakota Water Reports

Rapid City

≈ 180+ mg/L

🔴 Very Hard

Gillette

≈ 0–60 mg/L

🟢 Soft

Dickinson

≈ 120–179 mg/L

🟠 Hard

Scottsbluff

≈ 180+ mg/L

🔴 Very Hard

Report an Issue

Notice an error or missing data? Help us keep this page accurate. If you spot incorrect water hardness, outdated utility info, or missing details, please let us know.

All reports are reviewed by our team. Thank you for supporting data quality!

Frequently Asked Questions

Is Spearfish's water safe to drink?

Yes. Spearfish's water meets all federal safety standards. The hardness is ≈ 180+ mg/L (Very Hard), which is safe to drink. High hardness affects appliances and taste, but poses no health risk.

Do I need a water softener in Spearfish?

At ≈ 180+ mg/L (Very Hard), Spearfish's water will cause significant limescale on kettles, washing machines, and water heaters. A water softener or descaler is strongly recommended to extend appliance lifespan and reduce energy bills by up to 45%.

How does Spearfish compare to the USA average?

The USA national average is 151 mg/L. Spearfish (≈ 180+ mg/L) is 189 mg/L above the national average. The softest major city is Scarsdale at just 0.02 mg/L.

Data Sources & Methodology

Water quality data for Spearfish is derived from geographic and geological modelling of the surrounding region. No federal monitoring station data was available for this location.

Estimated

Water Hardness

Modelled estimate based on state-level USGS geological survey data for this region. No direct USGS Water Quality Portal measurement was matched to this city — the value reflects a statistical range calibrated to the state's dominant rock types and typical source water characteristics.

Estimated

Estimated from regional geology and source water characteristics. pH is correlated with water hardness and local bedrock — values may differ from utility-reported figures.

Estimated

TDS — Total Dissolved Solids

Estimated using a derived ratio from water hardness and regional conductance profiles. TDS in natural water correlates strongly with total mineral content including hardness ions.

Measured

PFAS — Perfluoroalkyl and Polyfluoroalkyl Substances

EPA UCMR5 (5th Unregulated Contaminant Monitoring Rule, 2023–2025) — sum of PFAS compounds detected at the public water system serving this city. A value of 0 indicates the system was sampled with no detection above reporting limits.

Modelled

Lead

Modelled estimate based on the EPA Lead and Copper Rule 90th-percentile tap-sample methodology. No publicly available per-city lead dataset with sufficient national coverage exists. Values are a conservative baseline derived from city population tier and infrastructure age — all estimates are maintained below the EPA action level of 0.015 mg/L.

Calculated

Appliance Lifespan

Calculated from water hardness using a linear degradation model. Baseline lifespans represent soft-water performance (kettle: 8.5 yrs, washing machine: 12.0 yrs, water heater: 15.0 yrs). Hard water mineral scale progressively reduces operational life in direct proportion to hardness concentration.