Water Quality Report · Updated October 07, 2026
ST CHARLES COUNTY PWSD 2
ST CHARLES COUNTY PWSD 2 delivers tap water graded C (65/100) by TapWaterSafety.org. The utility serves approximately 100,587 residents in O'FALLON, Missouri using surface water (purchased). The most significant water quality concerns are: Haloacetic acids (HAA9) significantly above health guideline; Arsenic* significantly above health guideline; Total trihalomethanes (TTHMs) significantly above health guideline. For questions, the utility can be reached at 636-385-5197.
Is O'FALLON tap water safe to drink?
ST CHARLES COUNTY PWSD 2 delivers tap water that earns a grade of C (65/100) from TapWaterSafety.org — an average rating, with several contaminants above health guidelines but generally compliant with US legal limits.
The utility serves 100,587 residents in O'FALLON, drawing from surface water (purchased). Despite being legal under US EPA standards, this water would fail the European Union's Drinking Water Directive, primarily due to haloacetic acids (haa9) significantly above health guideline.
Public testing data identifies 16 contaminants in this water above EWG's health-based guidelines, including: Haloacetic acids (HAA9), Arsenic*, Total trihalomethanes (TTHMs), Haloacetic acids (HAA5), Bromochloroacetic acid*, Bromodichloromethane, Chromium (hexavalent), Dichloroacetic acid, Chloroform, Radium, combined (-226 and -228), Trichloroacetic acid, Dibromoacetic acid, Dibromochloromethane, Nitrate*, Atrazine*, Nitrate and nitrite. For most residents, a properly certified home filter at the kitchen tap is the most cost-effective way to reduce exposure to whatever's in your water. See our filter recommendations below, matched specifically to this utility's contaminant profile.
EPA compliance record
Official U.S. EPA records for ST CHARLES COUNTY PWSD 2 (system ID MO6024530) for the last 3 years. Checked 2026-10-07.
| Rule | Type | Since | Status |
|---|---|---|---|
| Ground Water Rule | Missed testing or reporting | 06/01/2025 | Open |
Source: U.S. EPA Enforcement and Compliance History Online (ECHO), from the Safe Drinking Water Information System. See EPA's full report.
Quick actions for O'FALLON residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for ST CHARLES COUNTY PWSD 2.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 24.0 ppb, 399x above the EWG health guideline of 0.06 ppb.
Arsenic* significantly above health guideline
Moderate concernArsenic* detected at 0.736 ppb, 184x above the EWG health guideline of 0.004 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 24.9 ppb, 166x above the EWG health guideline of 0.15 ppb.
Contact ST CHARLES COUNTY PWSD 2
Reach the utility directly for service issues, water quality concerns, or to request your Consumer Confidence Report.
General Contact
Treatment Plant
Recommended water filters for O'FALLON
Filters matched to the specific contaminants in this water supply.
Carbon filter certified for VOCs (NSF/ANSI 53)
$180-$599Activated carbon is effective for disinfection byproducts. Look for NSF/ANSI 53 VOC reduction.
Reverse osmosis certified for arsenic (NSF/ANSI 58)
$429-$599Reverse osmosis certified under NSF/ANSI 58 for arsenic is the most reliable home option.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
Score breakdown
This utility's overall score of 65/100 breaks down across five weighted components. Read the full methodology →
Contaminants detected — international standards comparison
Every contaminant detected, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal (the strictest US benchmark). Why we show multiple standards →
| Contaminant | Detected | EWG US health-based |
EPA US legal |
EU DWD Europe |
WHO global |
CA PHG strictest US |
Tested sample year |
Status |
|---|---|---|---|---|---|---|---|---|
| Haloacetic acids (HAA9) Disinfection byproduct |
24.0 ppb | 0.06 | — | — | — | — | — | 399× over |
| Arsenic* Heavy metal |
0.736 ppb | 0.004 | 10.0 | 10 | 10 | 0.004 | — | 184× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
24.9 ppb | 0.15 | 80.0 | 100 | — | — | — | 166× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
14.1 ppb | 0.1 | 60.0 | 60 | — | — | — | 141× over |
| Bromochloroacetic acid* Disinfection byproduct |
2.03 ppb | 0.02 | — | — | — | — | — | 102× over |
| Bromodichloromethane Disinfection byproduct |
6.02 ppb | 0.06 | — | — | — | — | — | 100× over |
| Chromium (hexavalent) Heavy metal |
1.36 ppb | 0.02 | — | — | — | — | — | 68× over |
| Dichloroacetic acid Disinfection byproduct |
10.4 ppb | 0.2 | — | — | — | — | — | 52× over |
| Chloroform Disinfection byproduct |
15.6 ppb | 0.4 | — | — | — | — | — | 39× over |
| Radium, combined (-226 and -228) Radiological |
1.75 pCi/L | 0.05 | 5.0 | — | — | — | — | 35× over |
| Trichloroacetic acid Disinfection byproduct |
2.9 ppb | 0.1 | — | — | — | — | — | 29× over |
| Dibromoacetic acid Disinfection byproduct |
0.794 ppb | 0.03 | — | — | — | — | — | 26× over |
| Dibromochloromethane Disinfection byproduct |
2.63 ppb | 0.1 | — | — | — | — | — | 26× over |
| Nitrate* Inorganic |
1.02 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 7.3× over |
| Atrazine* Pesticide/Herbicide |
0.2 ppb | 0.1 | 3.0 | 0.1 | 100 | 0.15 | — | Fails EU |
| Nitrate and nitrite Inorganic |
0.164 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 1.2× over |
| Chlorate Disinfection byproduct |
207.1 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Bromoform Disinfection byproduct |
0.247 ppb | 0.5 | — | — | — | — | — | Below guideline |
| Antimony* Heavy metal |
0.315 ppb | 1.0 | 6.0 | 10 | 20 | 1 | — | Below guideline |
| Barium Heavy metal |
65.0 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| 1,4-Dioxane* Semi-volatile organic compound |
0.0288 ppb | 0.35 | — | — | 50 | 1 | — | Below guideline |
| Vanadium Other |
1.44 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Molybdenum Other |
2.63 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Selenium* Heavy metal |
1.64 ppb | 30.0 | 50.0 | 20 | 40 | 30 | — | Below guideline |
| Manganese Heavy metal |
4.95 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Monochloroacetic acid* Disinfection byproduct |
2.41 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Monobromoacetic acid* Disinfection byproduct |
0.157 ppb | 25.0 | — | — | — | — | — | Below guideline |
| Perfluorobutanoic Acid (PFBA) PFAS |
5.85 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Aluminum* Heavy metal |
2.15 ppb | 600.0 | — | 200 | — | 600 | — | Below guideline |
| Strontium Radiological |
0.213 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Chlorodifluoromethane Other |
0.0238 ppb | — | — | — | — | — | — | Below guideline |
| Chromium (total)* Heavy metal |
1.38 ppb | — | 100.0 | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.554 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| Lithium Other |
24.6 ppb | — | — | — | — | — | — | Below guideline |
| Nitrite* Inorganic |
0.0263 ppm | — | 1.0 | — | — | — | — | Below guideline |
| o-toluidine Other |
0.00138 ppb | — | — | — | — | — | — | Below guideline |
All values in the unit of the detected level. Red cells indicate the detected level exceeds that standard. Some contaminants have limits in some jurisdictions but not others (shown as —). The "Tested" column shows the year each contaminant sample was collected.
Sources: US EPA, EU Drinking Water Directive 2020/2184, WHO Guidelines (4th ed.), California OEHHA PHGs, EWG Tap Water Database.
ST CHARLES COUNTY PWSD 2 service area
This water system serves 1 community in St. Charles County, Missouri. Click any city for its dedicated tap water quality page.
Find the right filter for O'FALLON water
Browse filter categories by water-quality concern. Each option below is NSF-certified for the matched contaminant type.