How does O'Fallon's water compare to the national average?

The USA national average is 151 mg/L. O'Fallon (≈ 120–179 mg/L) is 1 mg/L softer than average.

O'Fallon Water Hardness & Quality Report (2026)

Water Hardness

hard

~120–179 mg/L

Hard

estimated · not lab-verified

Source

river

pH Level

7.2

neutral = 7.0

Lead

0.007 mg/L

✓ Below action level

TDS

797 mg/L

Est. Daily Cost

$0.40

energy & soap waste

Source: See methodology section below · Updated 2026

hard~120–179 mg/LHard · 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 O'Fallon, your appliances are currently losing 20% efficiency due to mineral buildup.

Appliance	In O'Fallon	Soft Water City	Efficiency Loss
Kettle	6.8 yrs	8.5 yrs	-20%
Washing Machine	9.6 yrs	12 yrs	-20%
Water Heater	12 yrs	15 yrs	-20%

Regional Water Comparison

How O'Fallon compares to its nearest neighbours

City	Hardness	PFAS (ppt)	Risk	Source
▶ O'Fallon, Illinois	≈ 120–179 mg/L	46.9 ppt	🟠 Hard	river
Shiloh, Illinois	≈ 120–179 mg/L	5.5 ppt	🟠 Hard	river
Fairview Heights, Illinois	≈ 180+ mg/L	8.2 ppt	🔴 Very Hard	river
Swansea, Illinois	≈ 120–179 mg/L	115.5 ppt	🟠 Hard	river
Belleville, Illinois	≈ 120–179 mg/L	4 ppt	🟠 Hard	river

National Benchmark

How O'Fallon compares to the USA average

Benchmark	Hardness	Appliance Risk
▶ O'Fallon	≈ 120–179 mg/L	🟠 Moderate
USA National Avg	151 mg/L	🟠 Moderate
Scarsdale Top Rated	0.02 mg/L	🟢 None

Bring Scarsdale-quality water to your O'Fallon home

Shop water softeners on Amazon.com →

Shop Now

What Makes O'Fallon's Water Unique?

Local geology and source profile

Source: RiverTDS: 797 mg/LpH: 7.2

The City of O'Fallon Water System serves 46,603 residents in O'Fallon, Illinois (St. Clair County). The utility purchases surface water from a bulk water provider and operates distribution infrastructure from City Hall at 255 South Lincoln Avenue, O'Fallon, IL 62269. Disinfection uses chloramines and sodium hypochlorite; no additional treatment is applied at the point of entry, relying on the quality of the purchased surface water.

O'Fallon's supply originates from surface sources within the Illinois River watershed, which drains terrain underlain by Ordovician and Silurian dolomite and limestone formations. These carbonate rock units are highly soluble, releasing dissolved calcium and magnesium into groundwater and surface runoff. The geological setting of southwestern Illinois produces a hard water supply typical of the region, shaped by the prevalence of limestone and dolomite aquifers.

Hard water causes scale buildup on faucet aerators, showerheads, and inside water heaters and dishwashers; soap and detergent efficiency drops, requiring higher doses for effective cleaning. A whole-house water softener is recommended; regular descaling of kettles and coffee makers extends their service life. O'Fallon's 2024 annual report records full USEPA compliance — pH 7.1–7.5 at entry point, chlorine residual 1.0–4 ppm, and lead levels well below EPA action levels.

Geology & Source: Southwestern Illinois — Illinois River watershed overlies Ordovician and Silurian dolomite and limestone; carbonate dissolution releases calcium and magnesium producing hard surface water

Other Illinois Water Reports

Shiloh

≈ 120–179 mg/L

🟠 Hard

Fairview Heights

≈ 180+ mg/L

🔴 Very Hard

Swansea

≈ 120–179 mg/L

🟠 Hard

Belleville

≈ 120–179 mg/L

🟠 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 O'Fallon's water safe to drink?

Yes. O'Fallon's water meets all federal safety standards. The hardness is ≈ 120–179 mg/L (Hard), which is safe to drink. High hardness affects appliances and taste, but poses no health risk.

Do I need a water softener in O'Fallon?

At ≈ 120–179 mg/L (Hard), O'Fallon'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 20%.

How does O'Fallon compare to the USA average?

The USA national average is 151 mg/L. O'Fallon (≈ 120–179 mg/L) is 1 mg/L below the national average. The softest major city is Scarsdale at just 0.02 mg/L.

Data Sources & Methodology

Water quality data for O'Fallon 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.