Is Fort Collins tap water safe to drink?

FT Collins City of uses free chlorine, according to its own water quality reporting. Free chlorine is the easy case: almost any carbon filter, from a basic pitcher to a shower filter, reduces the taste and smell.

Chlorine also reacts with natural organic matter in the water to form byproducts called trihalomethanes (THMs). EPA limits them because drinking water above the limit for many years may raise cancer risk. Your utility's annual water quality report lists its THM levels. A carbon filter certified to NSF/ANSI Standard 53 for THMs reduces them.

Fort Collins's water measures about 2.5 grains per gallon (42 mg/L as calcium carbonate), which is soft on the US Geological Survey scale: soft below 60 mg/L, moderately hard 60-120, hard 120-180, very hard above 180.

At this level a water softener is usually not worth the cost. Spend on filtration for taste or specific contaminants instead.

Hardness data: TapWaterData Water Hardness Dataset (tapwaterdata.com), licensed CC BY 4.0. Underlying source: Utility-reported water quality data — FT COLLINS CITY OF (PWSID CO0135291), 2025-08-27.

In FT Collins City of's most recent lead sampling, for the period ending December 2025, 90% of tested homes came in at or below 2.8 ppb of lead. That is low on any of the federal yardsticks.

This is a system-wide statistic, not a reading of your tap. Lead comes from lead service lines, old solder and some brass fixtures inside homes, so two houses on the same street can differ. Testing your own tap costs $15-40, and many utilities test free on request.

EPA's lead action level is 15 parts per billion (ppb) today and drops to 10 ppb in November 2027 under the Lead and Copper Rule Improvements. FDA's limit for bottled water is 5 ppb. EPA's health goal for lead is zero.

FT Collins City of was sampled in EPA's 2023-2025 nationwide survey, and none of the six regulated PFAS compounds were found above the lab reporting limits.

In April 2024 EPA set enforceable limits of 4 parts per trillion (ppt) for PFOA and PFOS, and 10 ppt for PFHxS, PFNA and HFPO-DA (GenX). In May 2025 EPA said it intends to keep the PFOA and PFOS limits, extend the compliance deadline to 2031, and rescind the other three. We compare results to the 2024 limits and label which ones may change.

EPA's records show 1 health-based violation for FT Collins City of since 2016: Interim Enhanced Surface Water Treatment Rule (1). The most recent began in December 2017.

A violation records a period when a standard or treatment requirement was missed. It is not a description of today's water, and many are resolved within the quarter. The utility's annual report explains each one.

Fort Collins is in Larimer County, which EPA places in Radon Zone 1: the predicted average indoor level is above 4 pCi/L, EPA's action level.

In Zone 1, testing is the single highest-value home health check you can do. A $15-25 charcoal kit gives an answer in a few days; a digital monitor shows how levels move with the seasons. If you measure 4 pCi/L or more, a mitigation system (typically $800-2,500) brings it down permanently.

EPA radon zones describe counties, not houses. Zone 1 counties have a predicted average indoor level above 4 picocuries per liter (pCi/L), Zone 2 between 2 and 4, Zone 3 below 2. Homes with high levels are found in every zone, which is why EPA recommends that every home be tested, and fixed at 4 pCi/L or above. See every Colorado county's radon zone.

From 2021-2025, EPA monitors in Larimer County rated 46.9% of days good. The air was unhealthy for sensitive groups or worse on about 19.8 days a year, more than 80% of monitored US counties. The pollutant behind most days was ozone, and the worst single reading was an AQI of 161 in 2024.

Wildfire smoke: NOAA satellites placed a medium or heavy smoke plume over Larimer County on about 19 days a year (51 in 2021, the worst year). That is below the typical US county.

EPA's Air Quality Index runs from 0 to 500. Up to 50 is good and 51-100 is moderate. Above 100 the air is unhealthy for sensitive groups (children, older adults, and people with asthma or heart or lung disease), and above 150 it is unhealthy for everyone. We count a county's bad days as days above 100, averaged over 2021-2025. Smoke days come from NOAA satellite analysts, who draw where smoke plumes are overhead each day. A plume overhead does not always reach the ground, so these days measure exposure risk, not what you breathed. We count only medium and heavy plumes.

Indoors, where you spend most of your time

No agency measures indoor air city by city, so nobody can tell you your home's numbers except a monitor in your home. What research does show: Americans spend about 90% of their time indoors (EPA's National Human Activity Pattern Survey, 2001), EPA studies in the 1980s often found indoor levels of some chemical vapors two to five times outdoor levels, and during wildfire smoke the particles get inside unless windows stay shut and a filter runs.

Air quality, smoke days and mold testing rules for every Colorado county. Sources: EPA AirData annual AQI by county, 2021-2025; NOAA Hazard Mapping System smoke polygons, 2021-2025.