Fairfax County, Virginia has about 1,160,925 residents (Census 2024 estimate) and 5 community water systems in EPA records. The largest local system is Fairfax County Water Authority, serving about 1,121,613 people from surface water.
✓ 0 of 5 largest systems with health-based violationsPFAS detected at 4 of 4 sampled systemsHardness 84–170 mg/L, varies by area
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 Fairfax County water?
Fairfax County Water AuthorityMeasured (utility report, n/a (FAQ page)) · High confidence
84–170 mg/L(varies by area; no single average published)
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.
At this hardness most homes don't need a softener. Confirm with a test strip if you see scale.
Largest water systems in Fairfax County
The 5 biggest of 5 community water systems on EPA records for this county. Service areas don't follow county lines; your water bill names your provider.
Fairfax County Water Authority
VA6059501 · serves about 1,121,613 people · Surface water
✓ No health-based violations✓ Lead below action levelPFAS detected (8 types)
Lead 90th percentile: 1.2 ppb (period starting 2021-01-01) Older result. Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
PFPeA: highest sample 21.5 ppt (10 of 24 samples); no federal limit
PFBA: highest sample 17.6 ppt (3 of 24 samples); no federal limit
PFHxA: highest sample 17.1 ppt (10 of 24 samples); no federal limit
6:2 FTS: highest sample 10.1 ppt (4 of 24 samples); no federal limit
PFBS: highest sample 8.1 ppt (5 of 24 samples); no individual limit; counted in EPA's PFAS mixture (hazard index) limit
PFOA: highest sample 7.4 ppt (3 of 24 samples); federal limit 4.0 ppt as a running annual average
PFOS: highest sample 5.7 ppt (2 of 24 samples); federal limit 4.0 ppt as a running annual average
PFHpA: highest sample 5.6 ppt (3 of 24 samples); no federal 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 Fairfax County water
Is tap water in Fairfax County safe to drink?
None of the 5 largest systems here have a health-based violation in EPA records since October 2021. Fairfax County Water Authority's most recent lead 90th percentile was 1.2 ppb (2021), 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 Fairfax County?
Fairfax County Water Authority reports hardness from 84 to 170 mg/L depending on where you live, with no single system-wide average, so check your area in its report or test your water.
Is there PFAS in Fairfax County water?
4 of the 4 sampled systems listed here detected at least one PFAS in EPA's UCMR 5 testing, and 4 results were above the level of a federal limit in at least one sample. A detection isn't a violation: federal PFAS limits apply to running annual averages starting in 2029.
Which water system serves my address in Fairfax County?
Most homes are served by Fairfax County Water Authority 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.