Hardness
Very Hard
332.5 PPM · 19.4 GPG
Local water dashboard
Official source aggregationWater quality in Knoxville, IA 50138
A source-transparent look at local hardness, associated public water systems, EPA compliance history, and the measurements that are—and are not—available for Marion County.
No active health-based violation reported
- Primary matched system
- Knoxville Water Works
- Source water
- Groundwater
- County
- Marion County
- Profile updated
At a glance
What the current records say
EPA quarter 2026Q2
Compliance screen
No active flag
0 active health-based records
Lead 90th percentile
0.0078 mg/L
52% of action level
Utility match
5 systems
Serves 8,400 people system-wide
Hardness meter
How hard is the water?
Estimated local hardness
USGS hardness classification scale
332.5 PPM
Soft
0–59Moderate
60–120Hard
121–180Very hard
181+
0–59Moderate
60–120Hard
121–180Very hard
181+
Parts per million
332.5
mg/L as CaCO₃ equivalent
Grains per gallon
19.4
1 GPG ≈ 17.1 PPM
What this means at home
At 332.5 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
16
Nearest site
15 mi
Observation range
May 30, 2017–Aug 1, 2024
Estimate confidence
Moderate
Median of the latest qualifying hardness observation at each nearby monitoring site. Nearest monitoring location: 077N18W08BBDC 1997NAWQA Marion Co IADRN-8 (Well).USGS source documentation ↗
Regional context
Is 50138 typical?
These comparisons use other indexed ZIP estimates, not utility tap samples. They help show local context without replacing a household test.
Knoxville median
333 PPM
About the same1 indexed ZIP readings · Range 332.5–332.5 PPM
Iowa median
281 PPM
52 PPM higher721 indexed ZIP readings · Range 182–834 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 pass
Lead (PB90)
0.0078 mg/L
Reported Dec 31, 2025
Copper (CU90)
Not available
No numerical 90th-percentile result
Numerical coverage
1 comparable result
Missing values remain blank; absence is not treated as a pass.
Lead (90th percentile)
Measured in mg/L
Local 0.0078
EPA limit 0.015
Share of EPA benchmark
100% line = listed limit
2026Q2
- All records
- 2
- Health-based
- 0
- Active health-based
- 0
| Contaminant or rule | System | Status | Period |
|---|---|---|---|
| Public Notice | IA6342711 | Unaddressed | Jan 21, 2025 |
| Nitrite | IA6342711 | Resolved | Oct 1, 2023through Sep 30, 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 Knoxville ZIP 50138 using 332.5 PPM nearby hardness and 1 reported measurement benchmarks.
Scale protection
High-Capacity Whole House Water Softener
332.5 PPM is 3× 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 systemsAffiliate 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.
Frequently asked
Water questions for Knoxville
Is tap water safe in Knoxville?+
EPA ECHO shows no active health-based violation for the associated systems in this reporting snapshot. This does not prove every contaminant is absent; federal records can lag and household plumbing can change tap conditions.
How hard is the water?+
Nearby USGS observations produce an estimate of 332.5 PPM, or 19.4 grains per gallon, classified as very hard. This is not a household tap measurement.
Do I need a water softener?+
At 332.5 PPM, a correctly sized whole-house softener can reduce scale and hard-water spotting. It does not replace contaminant filtration.