Longmont, CO: 12 Violations — 62/100 (2026)
4 ZIP codes · 14 water systems · Updated 2026-06-03
Water systems across Longmont produce average compliance results for CO overall — pockets with documented violations exist, and the variation between areas makes checking the specific system serving a given address the most useful step for residents here.
How Longmont Compares
Data: EPA SDWIS Last verified: 2026-06-03
Longmont Water: The Quick Version
- Your city's water systems recorded 12 violations in the past 5 years.
- Average lead level: 0.0016 mg/L.
- Homes built before 1986: 43% — older plumbing may contain lead solder.
- Estimated remediation: $3,025 per household.
- CDC health risk index: 9.34.
Water Systems Serving Longmont
Residential addresses in Longmont, CO are served by 3 primary water providers out of 14 systems in federal records. Each system maintains separate infrastructure and files its own EPA compliance reports, so service conditions are not uniform across the city.
Overview
We track water quality and home safety data for 4 ZIP codes in Longmont, Colorado (population ~141,102), covering 14 community water systems serving approximately 429,735 people region-wide.
4 of 4 ZIP codes (100%) have recorded EPA violations. All violations are monitoring/reporting type.
Home Safety Score
Average Home Safety Score for Longmont: C (62/100)
The score combines three factors:
| Factor | What It Measures |
|---|---|
| Water Quality | EPA violations and compliance history |
| Lead Levels | 90th percentile lead concentration vs EPA action level |
| Radon Risk | EPA radon zone classification |
Water Sources
Longmont water systems draw from: Surface water.
Lead & Copper
- Average lead level (90th percentile): 0.0016 mg/L (EPA action level: 0.015 mg/L)
- 0 ZIP codes exceed the EPA lead action level
Radon Risk
Dominant radon zone: Zone 1 (High Risk)
- Zone 1 (High): 4 ZIP codes
- Zone 2 (Moderate): 0 ZIP codes
- Zone 3 (Low): 0 ZIP codes
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Top Contaminants
| Contaminant | Category | Violations | ZIPs Affected |
|---|---|---|---|
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 5 | 4 |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 5 | 4 |
| Stage 2 DBP Rule | Treatment Technique | 5 | 4 |
Areas with Most Violations
| ZIP Code | Safety Score | Violations | Health-Based | System |
|---|---|---|---|---|
| 80501 | C | 3 | 0 | City of Longmont |
| 80502 | C | 3 | 0 | City of Longmont |
| 80503 | C | 3 | 0 | City of Longmont |
| 80504 | C | 3 | 0 | City of Longmont |
All ZIP Codes in Longmont
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
Updated daily.
CDC Health Data for Longmont
Source: CDC PLACES (County-level estimates). Water contamination can correlate with respiratory and chronic health conditions.
Compared to National Average
Vertical line = national average. ■ Above national · ■ Below national
Key Contaminants Detected in Longmont
Based on EPA violation records. Check your ZIP code report for system-specific contaminant data.
How Old Is Longmont's Housing Stock?
With 43% of homes built before 1986, lead solder in plumbing is a potential concern. The EPA banned lead solder in 1986, but many older homes retain original plumbing.
Source: U.S. Census Bureau American Community Survey (ACS).
Housing Age Profile
Over the decades, Longmont accumulated housing from multiple construction periods. The median build year of 1992 places the midpoint of that stock near the 1986 threshold when lead solder in plumbing became federally prohibited — leaving a sizable share of homes on each side of that safety line.
Most homes in Longmont were built after 1986, reducing the risk of lead contamination from plumbing. Older homes should still be tested.
Source: U.S. Census Bureau ACS B25034.
Longmont: Remediation Cost in Perspective
Remediation costs in Longmont are small relative to typical property values — the cost-to-value ratio here is favorable.
Remediation costs in Longmont are relatively low compared to home values. The $2,050–$4,150 estimated range is a small fraction of median property value. Home values are 23% above the Colorado average.
Protecting Children from Lead in Longmont
Why children are most at risk: The CDC states there is no safe level of lead exposure for children. Children under 6 absorb lead more readily than adults, and even low levels can cause developmental delays, learning difficulties, and behavioral problems.
Before the federal solder ban, lead solder was a routine plumbing material, and 43% of the Longmont inventory was built in that earlier era — a share large enough to move household-level reads onto the standard list.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
Climate-Related Water Risk for Longmont
Multiple flood events have been recorded for Longmont through the NFIP — 142 claims in total, with 75% of ZIP codes in FEMA-designated zones — pointing to a flood exposure profile that merits inclusion in a water quality assessment without reaching high-severity planning territory.
Longmont has a moderate flood history with 142 FEMA claims averaging $48,417 per payout. 75% of ZIP codes fall within FEMA flood zones. Flood events can contaminate drinking water and overwhelm treatment systems.
How flooding affects water quality: Flood events can introduce sewage, agricultural runoff, and industrial chemicals into water supplies. Even after floodwaters recede, contamination can persist in wells and aging infrastructure. Flood damage can add significantly to the estimated <strong>$3,025</strong> remediation cost per household.
Residents in flood-prone areas should consider flood insurance even outside FEMA zones — over 25% of flood claims come from low-to-moderate risk areas. After any flood event, test your water before drinking.
Source: FEMA National Flood Insurance Program (NFIP) claims data, FEMA flood zone designations.
What You Can Do in Longmont
- Test your water at home. City-level data shows averages — your tap may differ. NSF-certified test kits cost $20-40 and give results in days.
- Install a certified water filter. Filters rated for Total Trihalomethanes (TTHM) can reduce the most common contaminant found in Longmont's water.
- Check your home's plumbing. With 43% of homes built before 1986, lead solder is a real possibility.
Deep Dive Reports
Detailed analysis for Longmont, CO