Hardness
Very Hard
615 PPM · 36 GPG
Local water dashboard
Official source aggregationWater quality in Rapid City, SD 57703
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
- Rapid Valley Sanitary District
- Source water
- Surface water + Groundwater
- 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
3 systems
Serves 11,408 people system-wide
Hardness meter
How hard is the water?
Estimated local hardness
USGS hardness classification scale
615 PPM
Soft
0–59Moderate
60–120Hard
121–180Very hard
181+
0–59Moderate
60–120Hard
121–180Very hard
181+
Parts per million
615
mg/L as CaCO₃ equivalent
Grains per gallon
36
1 GPG ≈ 17.1 PPM
What this means at home
At 615 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
11
Nearest site
7.1 mi
Observation range
Jan 5, 2016–Mar 18, 2026
Estimate confidence
Moderate
Median of the latest qualifying hardness observation at each nearby monitoring site. Nearest monitoring location: BOXELDER CREEK AT 151ST AVE NR BOX ELDER, SD (Stream).USGS source documentation ↗
Regional context
Is 57703 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
About the same3 indexed ZIP readings · Range 525.5–615 PPM
South Dakota median
516 PPM
99 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)
Not available
No numerical 90th-percentile result
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
Combined Radium (-226 and -228)
Measured in PCI/L
Local 13
EPA limit 5
Gross Alpha, Excl. Radon and U
Measured in PCI/L
Local 25
EPA limit 15
Share of EPA benchmark
100% line = listed limit
2026Q2
- All records
- 6
- Health-based
- 6
- Active health-based
- 1
| Contaminant or rule | System | Status | Period |
|---|---|---|---|
| Combined Radium (-226 and -228)Health-basedReported 13 PCI/L · MCL 5 | SD4600403 | Archived | Jan 1, 2026through Mar 31, 2026 |
| Gross Alpha, Excl. Radon and UHealth-basedReported 25 PCI/L · MCL 15 | SD4600403 | Archived | Jan 1, 2026through Mar 31, 2026 |
| Stage 1 Disinfectants and Disinfection Byproducts RuleHealth-based | SD4600403 | Unaddressed | Nov 12, 2025 |
| Combined Radium (-226 and -228)Health-basedReported 10 PCI/L · MCL 5 | SD4600403 | Archived | Oct 1, 2025through Dec 31, 2025 |
| Combined Radium (-226 and -228)Health-basedReported 7 PCI/L · MCL 5 | SD4600403 | Archived | Jul 1, 2025through Sep 30, 2025 |
| Stage 1 Disinfectants and Disinfection Byproducts RuleHealth-based | SD4602301 | Resolved | Feb 1, 2025through May 22, 2025 |
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 57703 using 615 PPM nearby hardness and 3 reported measurement benchmarks.
Scale protection
High-Capacity Whole House Water Softener
615 PPM is 5× 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
Combined Radium (-226 and -228), 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 615 PPM, or 36 grains per gallon, classified as very hard. This is not a household tap measurement.
Do I need a water softener?+
At 615 PPM, a correctly sized whole-house softener can reduce scale and hard-water spotting. It does not replace contaminant filtration.