Hardness
Very Hard
525.5 PPM · 30.7 GPG
Local water dashboard
Official source aggregationWater quality in Rapid City, SD 57702
A source-transparent look at local hardness, associated public water systems, EPA compliance history, and the measurements that are—and are not—available for Pennington County.
1 active health-based violation
- Primary matched system
- Colonial Pine Hills Sanitary Distric
- Source water
- Groundwater + Groundwater influenced by surface water
- County
- Pennington County
- Profile updated
At a glance
What the current records say
EPA quarter 2026Q2
Compliance screen
Review needed
1 active health-based record
Lead 90th percentile
0.001 mg/L
7% of action level
Utility match
10 systems
Serves 1,200 people system-wide
Hardness meter
How hard is the water?
Estimated local hardness
USGS hardness classification scale
525.5 PPM
Soft
0–59Moderate
60–120Hard
121–180Very hard
181+
0–59Moderate
60–120Hard
121–180Very hard
181+
Parts per million
525.5
mg/L as CaCO₃ equivalent
Grains per gallon
30.7
1 GPG ≈ 17.1 PPM
What this means at home
At 525.5 PPM, mineral scale can build up on fixtures and heating elements, reduce soap lather, and leave visible spotting. Hardness is primarily an aesthetic and appliance concern—not itself a tap-water safety rating.
USGS sites used
22
Nearest site
10.8 mi
Observation range
May 9, 2016–Nov 20, 2024
Estimate confidence
Moderate
Median of the latest qualifying hardness observation at each nearby monitoring site. Nearest monitoring location: 002S06E18BD (Burnpit well) (Well).USGS source documentation ↗
Regional context
Is 57702 typical?
These comparisons use other indexed ZIP estimates, not utility tap samples. They help show local context without replacing a household test.
Rapid City median
615 PPM
89 PPM lower3 indexed ZIP readings · Range 525.5–615 PPM
South Dakota median
516 PPM
10 PPM higher234 indexed ZIP readings · Range 20.5–1330 PPM
EPA benchmark screen
Contaminant snapshot
Available numerical results from associated SDWIS community water systems, compared with the applicable action level or federal MCL. Federal measured-value coverage is incomplete.
1 pass2 fail
Lead (PB90)
0.001 mg/L
Reported Dec 31, 2025
Copper (CU90)
4 mg/L
Reported Jun 30, 2008
Numerical coverage
3 comparable results
Missing values remain blank; absence is not treated as a pass.
Lead (90th percentile)
Measured in mg/L
Local 0.001
EPA limit 0.015
Copper (90th percentile)
Measured in mg/L
Local 4
EPA limit 1.3
Gross Alpha, Excl. Radon and U
Measured in PCI/L
Local 16
EPA limit 15
Share of EPA benchmark
100% line = listed limit
2026Q2
- All records
- 46
- Health-based
- 5
- Active health-based
- 1
| Contaminant or rule | System | Status | Period |
|---|---|---|---|
| Revised Total Coliform Rule | SD4602209 | Archived | Jan 1, 2026through Jan 31, 2026 |
| Stage 1 Disinfectants and Disinfection Byproducts RuleHealth-based | SD4600420 | Unaddressed | Jul 7, 2025 |
| Revised Total Coliform Rule | SD4600050 | Resolved | Jul 1, 2025through Jul 31, 2025 |
| Revised Total Coliform Rule | SD4602209 | Resolved | Nov 1, 2024through Nov 30, 2024 |
| Revised Total Coliform Rule | SD4600050 | Resolved | Oct 1, 2024through Oct 31, 2024 |
| Revised Total Coliform Rule | SD4600269 | Resolved | Oct 1, 2024through Oct 31, 2024 |
| Revised Total Coliform Rule | SD4602209 | Resolved | Aug 1, 2024through Aug 31, 2024 |
| Consumer Confidence Rule | SD4602209 | Unaddressed | Jul 1, 2024 |
| Stage 1 Disinfectants and Disinfection Byproducts RuleHealth-based | SD4602209 | Resolved | May 21, 2024through Oct 30, 2025 |
| Public Notice | SD4602209 | Resolved | Mar 9, 2024through Dec 26, 2024 |
| Public Notice | SD4602209 | Resolved | Mar 9, 2024through May 3, 2024 |
| Revised Total Coliform Rule | SD4602209 | Resolved | Mar 1, 2024through Mar 31, 2024 |
| Revised Total Coliform Rule | SD4602209 | Resolved | Feb 1, 2024through Feb 29, 2024 |
| Vinyl chloride | SD4602209 | Resolved | Jan 1, 2024through Dec 31, 2024 |
| 1,1,1-Trichloroethane | SD4602209 | Resolved | Jan 1, 2024through Dec 31, 2024 |
| Tetrachloroethylene | SD4602209 | Resolved | Jan 1, 2024through Dec 31, 2024 |
| Ethylbenzene | SD4602209 | Resolved | Jan 1, 2024through Dec 31, 2024 |
| DICHLOROMETHANE | SD4602209 | Resolved | Jan 1, 2024through Dec 31, 2024 |
| 1,2,4-Trichlorobenzene | SD4602209 | Resolved | Jan 1, 2024through Dec 31, 2024 |
| Xylenes, Total | SD4602209 | Resolved | Jan 1, 2024through Dec 31, 2024 |
No reported violation does not prove that every contaminant was tested or absent; SDWIS measured values are incomplete and lag state records.
Solutions matcher
Your personalized water action plan
Matched to Rapid City ZIP 57702 using 525.5 PPM nearby hardness and 3 reported measurement benchmarks.
Scale protection
High-Capacity Whole House Water Softener
525.5 PPM is 4× the high-hardness trigger used by this matcher.
Designed to reduce scale on fixtures, water heaters, glassware, and plumbing throughout the home.
Compare whole-house systemsDrinking water protection
Under-Sink Reverse Osmosis System
Copper (90th percentile), Gross Alpha, Excl. Radon and U, Stage 1 Disinfectants and Disinfection Byproducts Rule have a measured benchmark flag or active health-based SDWIS record in this profile.
A certified multi-stage RO system targets a broader range of dissolved contaminants at the kitchen tap.
Explore under-sink filtrationAffiliate disclosure: we may earn a commission from qualifying purchases, at no added cost to you. Product matching is educational and does not replace certified water testing.
Nearby indexed reports
Compare ZIPs in Rapid City
Estimates can differ across a city because monitoring locations and associated systems differ.
Frequently asked
Water questions for Rapid City
Is tap water safe in Rapid City?+
EPA ECHO reports 1 active health-based violation among the associated community water systems. Review the affected utility's current notice and Consumer Confidence Report.
How hard is the water?+
Nearby USGS observations produce an estimate of 525.5 PPM, or 30.7 grains per gallon, classified as very hard. This is not a household tap measurement.
Do I need a water softener?+
At 525.5 PPM, a correctly sized whole-house softener can reduce scale and hard-water spotting. It does not replace contaminant filtration.