Tap Water Quality Report
Tap water quality in LONGMONT, Colorado
Tap water in LONGMONT, Colorado receives a grade of B (82/100) from TapWaterSafety.org. It's served by LONGMONT CITY OF. The most significant water quality concerns are: Haloacetic acids (HAA9) significantly above health guideline; Total trihalomethanes (TTHMs) significantly above health guideline; Haloacetic acids (HAA5) significantly above health guideline. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.
What's in LONGMONT's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving LONGMONT.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 24.0 ppb, 400x above the EWG health guideline of 0.06 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 30.6 ppb, 204x above the EWG health guideline of 0.15 ppb.
Haloacetic acids (HAA5) significantly above health guideline
Moderate concernHaloacetic acids (HAA5) detected at 18.7 ppb, 187x above the EWG health guideline of 0.1 ppb.
EPA compliance record
Official U.S. EPA records for LONGMONT CITY OF (system ID CO0107485) for the last 3 years. Checked 2026-10-07.
Source: U.S. EPA Enforcement and Compliance History Online (ECHO), from the Safe Drinking Water Information System. See EPA's full report.
Recommended filters for LONGMONT
Filters matched to the specific contaminants in LONGMONT's 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.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
All contaminants detected in LONGMONT's tap water
Every contaminant identified, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal. 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 | — | — | — | — | — | 400× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
30.6 ppb | 0.15 | 80.0 | 100 | — | — | — | 204× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
18.7 ppb | 0.1 | 60.0 | 60 | — | — | — | 187× over |
| Trichloroacetic acid Disinfection byproduct |
10.0 ppb | 0.1 | — | — | — | — | — | 100× over |
| Chloroform Disinfection byproduct |
28.1 ppb | 0.4 | — | — | — | — | — | 70× over |
| Dichloroacetic acid Disinfection byproduct |
8.52 ppb | 0.2 | — | — | — | — | — | 43× over |
| Bromodichloromethane Disinfection byproduct |
2.53 ppb | 0.06 | — | — | — | — | — | 42× over |
| Chromium (hexavalent) Heavy metal |
0.0428 ppb | 0.02 | — | — | — | — | — | 2.1× over |
| Chlorate Disinfection byproduct |
95.4 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Nitrate Inorganic |
0.0367 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | Below guideline |
| Manganese Heavy metal |
2.54 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.113 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.0383 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.67 ppm | — | 4.0 | 1.5 | 1.5 | — | — | 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, California OEHHA PHGs, EWG Tap Water Database.
Treatment plant contact info
For service issues, water quality concerns, or to request a Consumer Confidence Report from LONGMONT CITY OF.