Collin County, Texas has about 1,254,658 residents (Census 2024 estimate) and 35 community water systems in EPA records. The largest local system is City of Plano, serving about 292,059 people from surface water.
✓ 0 of 6 largest systems with health-based violationsPFAS detected at 6 of 6 sampled systemsHardness 7.8 gpg (low confidence)
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
How hard is Collin County water?
City of PlanoEstimate: untreated local water, not your tap · Low confidence
7.8 gpg(134 mg/L), hard
Collin County: median of 503 results from 23 monitoring sites (streams and wells). Utilities may blend or treat water, so your tap can differ.
County estimates: Hard Water Map (hardwatermap.com), CC BY 4.0, derived from the USGS/EPA Water Quality Portal; file generated 2026-07-22. License
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
Softener size at 7.8 gpg
For a 3-person home using 57 gallons per person per day and regenerating weekly, you'd remove about 9,337 grains between regenerations. Suggested size: 24,000 grain. This uses a low-confidence county estimate, so confirm with a test first.
Estimate only. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
The 6 biggest of 35 community water systems on EPA records for this county. Service areas don't follow county lines; your water bill names your provider.
City of Plano
TX0430007 · serves about 292,059 people · Surface water
✓ No health-based violations✓ Lead below action levelPFAS detected (4 types)
Lead 90th percentile: 1.7 ppb (period starting 2026-01-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
PFBA: highest sample 7.3 ppt (2 of 4 samples); no federal limit
PFHxA: highest sample 4.4 ppt (4 of 4 samples); no federal limit
PFPeA: highest sample 4.3 ppt (4 of 4 samples); no federal limit
PFBS: highest sample 3.1 ppt (1 of 4 samples); no individual limit; counted in EPA's PFAS mixture (hazard index) limit
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
A PFAS detection is not a violation. Federal limits (4 ppt for PFOA and PFOS) apply to running annual averages, with compliance required by 2029. In May 2026 EPA proposed extending the PFOA/PFOS deadline to 2031 and removing other PFAS limits; not final as of 2026-10-21.
Test your own tap
These are public records for whole systems. Your home's pipes, fixtures and any private well can change what you drink. A certified lab test or a hardness test strip gives you your own numbers. Then use our PFAS and lead filter selector to see which certifications to look for.
Common questions about Collin County water
Is tap water in Collin County safe to drink?
None of the 6 largest systems here have a health-based violation in EPA records since October 2021. City of Plano's most recent lead 90th percentile was 1.7 ppb (2026), below the 15 ppb action level. Public records can't guarantee what comes out of your tap, especially with older plumbing, so a home test is the surest check.
How hard is the water in Collin County?
There's no published utility figure in our data, but untreated local stream and well samples in Collin County have a median of about 7.8 grains per gallon (134 mg/L, hard). That's a low-confidence estimate of source water, not your tap, so test before you buy equipment. For a 3-person home at 7.8 gpg, our softener calculator suggests a 24,000 grain unit as a starting point.
Is there PFAS in Collin County water?
6 of the 6 sampled systems listed here detected at least one PFAS in EPA's UCMR 5 testing. A detection isn't a violation: federal PFAS limits apply to running annual averages starting in 2029.
Which water system serves my address in Collin County?
Most homes are served by City of Plano or one of the other systems listed on this page, but service areas don't follow county lines. Your water bill names your provider, and its annual Consumer Confidence Report has the full test results.
Data as of October 21, 2026. Figures are copied from public records and combined with our own calculations; they can be out of date or wrong. Tapped Out isn't affiliated with any utility or the EPA. Written and reviewed by the Tapped Out team. How we calculate · All sources.