Collin County, Texas: drinking water report. Collin County sits north of Dallas and is one of the fastest-growing counties in the country, with a
Collin County sits north of Dallas and is one of the fastest-growing counties in the country, with a population now exceeding 1.1 million. Water comes primarily from the North Texas Municipal Water District (NTMWD), which draws from Lavon Lake, Lake Texoma, and other regional reservoirs. The rapid pace of development – McKinney, Frisco, and Plano have all seen explosive growth – means water infrastructure is constantly playing catch-up with demand.
NTMWD's surface water sources are generally clean, drawing from reservoirs in the blackland prairie region of north Texas. UCMR5 data shows low-level PFAS detections in county water systems, consistent with diffuse contamination rather than point sources. The district does not have major military installations or heavy industrial facilities in its immediate watershed.
The primary quality concern in Collin County is taste and hardness. North Texas water from these reservoirs carries high total dissolved solids and mineral content. According to the NTMWD's 2024 water quality report, TDS levels averaged around 450 mg/L – above the EPA's secondary standard of 500 mg/L at some monitoring points. While not a health hazard, this affects taste and creates scale buildup in home plumbing and appliances.
Collin County's water is generally safe by federal standards, but hardness and taste are common complaints. Rapid growth also means new neighborhoods may experience water quality variability as new mains are flushed and stabilized.
Check your water for the latest monitoring data in your area. A whole-house softener addresses hardness, while a reverse osmosis system under the sink improves taste and removes PFAS. Our water filter guide covers both scenarios. Pull your detailed report, and see our Texas page for statewide data.
Drinking water is one exposure route. These federal datasets also cover Collin County, TX.
The EPA places Collin County, TX in Zone 3 - the EPA's lowest-risk category, with a predicted average indoor radon level below 2 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
12% of homes in Collin County, TX were built before 1980, and 1% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Collin County, TX averages 9 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide
Across 35 public water systems serving Collin County, TX with EPA lead testing on record, 0 (0%) reported a 90th-percentile lead result above the EPA's 15 ppb action level, and the median is 2.7 ppb. 7 water systems serving Collin County, TX carry a health-based EPA Safe Drinking Water Act violation.
| Most-cited violation type | Systems affected |
|---|---|
| Total Coliform Rule | 3 |
| Total Trihalomethanes (TTHM) | 2 |
| Lead and Copper Rule Revisions | 2 |
| Haloacetic Acids (HAA5) | 1 |
| Interim Enhanced Surface Water Treatment Rule | 1 |
Source: EPA Lead and Copper Rule 90th-percentile tap sampling and EPA SDWIS Safe Drinking Water Act enforcement records, aggregated from the public water systems serving this county. Figures are counts of water systems, not a test of any individual home or tap.