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

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

Cahokia Water Hardness & Quality Report (2026)

Water Hardness

very hard

180+ mg/L

Very Hard

estimated · not lab-verified

Source

river

pH Level

8.2

neutral = 7.0

Lead

0.005 mg/L

✓ Below action level

TDS

409.8 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 Cahokia, your appliances are currently losing 45% efficiency due to mineral buildup.

Appliance	In Cahokia	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 Cahokia compares to its nearest neighbours

City	Hardness	PFAS (ppt)	Risk	Source
▶ Cahokia, Illinois	≈ 180+ mg/L	63.2 ppt	🔴 Very Hard	river
St. Louis, Missouri	≈ 60–120 mg/L	3 ppt	🟡 Moderately Hard	river
East Saint Louis, Illinois	≈ 120–179 mg/L	6.9 ppt	🟠 Hard	river
Lemay, Missouri	≈ 120–179 mg/L	5.8 ppt	🟠 Hard	river
Columbia, Illinois	283 mg/L	41.7 ppt	🔴 Very Hard	river

National Benchmark

How Cahokia compares to the USA average

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

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What Makes Cahokia's Water Unique?

Local geology and source profile

Source: RiverTDS: 409.8 mg/LpH: 8.2

Cahokia Heights, Illinois, receives its water from Illinois American Water and the Cahokia Heights municipal water utility, serving residents in St. Clair County. The water comes from a mix of surface and groundwater sources within the Illinois River watershed. Both utilities operate treatment plants that use conventional disinfection and chemical treatment methods to prepare the water for distribution.

The region's water originates from Quaternary glacial deposits resting above Paleozoic bedrock. This bedrock is composed of Ordovician and Silurian dolomites and limestones. As water flows through these soluble carbonate formations, it picks up calcium and magnesium, leading to the very hard water characteristic of the area. The Illinois River watershed itself contributes to this mineral content.

Residents of Cahokia Heights often notice significant scale buildup on faucets, showerheads, water heaters, and inside pipes. This mineral accumulation can reduce the efficiency of appliances like dishwashers and washing machines, requiring more frequent maintenance and potentially shortening their lifespan. For those looking to combat these issues, a water softening system is a worthwhile investment. It can help reduce maintenance costs, extend the life of appliances, and improve the lathering of soaps and detergents. Recent testing by Equity Legal Services in March 2026 also highlighted serious concerns, including detections of total coliform and E. coli, low chlorine residuals, and the presence of arsenic, chromium-6, and trihalomethanes.

Geology & Source: Illinois River watershed Quaternary glacial deposits; Paleozoic dolomites and limestones produce very hard water

Other Illinois Water Reports

St. Louis

≈ 60–120 mg/L

🟡 Moderately Hard

East Saint Louis

≈ 120–179 mg/L

🟠 Hard

Lemay

≈ 120–179 mg/L

🟠 Hard

Columbia

283 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 Cahokia's water safe to drink?

Yes. Cahokia'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 Cahokia?

At ≈ 180+ mg/L (Very Hard), Cahokia'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 Cahokia compare to the USA average?

The USA national average is 151 mg/L. Cahokia (≈ 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 Cahokia 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.