Water Quality Report · Updated May 12, 2026
LONGMONT CITY OF
LONGMONT CITY OF delivers tap water graded C (67/100) by TapWaterSafety.org. The utility serves approximately 102,866 residents in LONGMONT, Colorado using surface water. 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. For questions, the utility can be reached at 303-651-8351.
Is LONGMONT tap water safe to drink?
LONGMONT CITY OF delivers tap water that earns a grade of C (67/100) from TapWaterSafety.org — an average rating, with several contaminants above health guidelines but generally compliant with US legal limits.
The utility serves 102,866 residents in LONGMONT, drawing from surface water.
Public testing data identifies 8 contaminants in this water above EWG's health-based guidelines, including: Haloacetic acids (HAA9), Total trihalomethanes (TTHMs), Haloacetic acids (HAA5), Trichloroacetic acid, Chloroform, Dichloroacetic acid, Bromodichloromethane, Chromium (hexavalent). 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.
Quick actions for LONGMONT residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for LONGMONT CITY OF.
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.
Contact LONGMONT CITY OF
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 LONGMONT
Filters matched to the specific contaminants in this water supply.
Carbon block (NSF/ANSI 42 + 53)
$40-$750Activated carbon is highly effective for disinfection byproducts like TTHM and HAA5.
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 67/100 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 | — | — | — | — | — | 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 (4th ed.), California OEHHA PHGs, EWG Tap Water Database.
LONGMONT CITY OF service area
This water system serves 1 community in Boulder County, Colorado. Click any city for its dedicated tap water quality page.
Find the right filter for LONGMONT water
Browse filter categories by water-quality concern. Each option below is NSF-certified for the matched contaminant type.