Loudoun Water – Central System water quality
Ashburn, VA · serves 334,808 people (83,426 connections) · Surface water · Local government · EPA ID VA6107350
Data: U.S. EPA · How we read the data · How we check it
Buys water from Fairfax County Water Authority. Treated water bought from another system can carry that system's contaminants.
Summary
No federal limits exceeded in EPA data.
- PFAS
- Detected, below limit1 of 29 PFAS found at least once. All averages below the federal limits.
- Lead
- Below action level0.5 ppb (parts per billion) at the 90th percentile: 9 in 10 homes sampled were at or below it. Action level 15 ppb, falling to 10 ppb in Nov 2027. Monitoring period Jan 2024 – now, still in progress (results reported so far). Your home's pipes can make yours higher.
- Violations
- None health-basedNo health-based violations since 2016.
- Built before 1986, or not sure what your service line is made of? Check your service line and test your tap. Utility data can't show your pipes.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read Loudoun Water – Central System's 2026 water quality report (Consumer Confidence Report, from the utility). It lists every regulated contaminant tested, including ones not on this page. Questions: (571) 291-7844.
PFAS (“forever chemicals”)
EPA UCMR 5: 2 entry points tested Jun 2023 to Mar 2024. "Average" is the highest entry-point average (non-detects counted as zero), the way EPA compares UCMR 5 results to the limits. ppt = parts per trillion. These results do not determine compliance.
| Contaminant | Highest average |
|---|---|
| PFOA Not detected Limit 4 ppt | – |
| PFOS Not detected Limit 4 ppt | – |
| PFHxS Not detected Limit 10 ppt | – |
| PFNA Not detected Limit 10 ppt | – |
| HFPO-DA (GenX) Not detected Limit 10 ppt | – |
| Hazard Index (a combined score for PFHxS, PFNA, GenX and PFBS, where above 1 is over the limit) Not detected Limit 1 | – |
| PFBS Not detected Guideline 2,000 ppt | – |
| PFBA Not detected Guideline 6,000 ppt | – |
| PFHxA Not detected Guideline 3,000 ppt | – |
| PFPeA Detected, no limit | 0.85 ppt |
29 PFAS tested, 1 detected at least once. "Not detected" means below EPA's reporting limit (about 2 to 20 ppt depending on the chemical), not proven zero. PFAS not listed were not detected. The limits for PFHxS, PFNA, GenX and the Hazard Index were proposed for rescission in May 2026. That proposal is not final. Systems have until 2029 to meet the limits.
Lithium
Not detected in 8 samples (reporting limit 9 ppb). About lithium.
Lead and copper
Latest 90th percentile: 0.5 ppb lead (Jan 2024 – now (in progress)). Below action level
Highest since 2016: 1.1 ppb (Dec 2017).
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2024 – now (in progress) | 0.5 ppb |
| Jan 2021 – Dec 2023 | 0 ppb |
| Jan 2018 – Dec 2020 | 0 ppb |
Earlier results (9)
| Jan 2015 – Dec 2017 | 1.1 ppb |
| Jan 2012 – Dec 2014 | 0.5 ppb |
| Jan 2009 – Dec 2011 | 2 ppb |
| Jul 2007 – Dec 2007 | 0.1 ppb |
| Jan 2007 – Jun 2007 | 0 ppb |
| Jan 2003 – Dec 2005 | 1 ppb |
| Jan 2002 – Dec 2002 | 1 ppb |
| Jan 2001 – Dec 2001 | 1 ppb |
| Jan 2000 – Jun 2000 | 8 ppb |
Lead comes from pipes and fixtures, not the source water, so it varies home to home. The 90th percentile means 9 in 10 sampled homes were at or below it. More on lead.
Violations
Health-based violations mean a contaminant exceeded a limit or a required treatment step was missed. Monitoring and reporting violations mean required tests or reports were late or missing, so the water's quality during that time is unknown. The total includes every violation in EPA's records, most of them paperwork.
Earlier EPA testing (2013–2020)
| Contaminant | Highest | Guideline |
|---|---|---|
| Manganese | 4.2 ppb | 300 ppb |
| Chlorate | 200 ppb | 210 ppb |
| Vanadium | 0.64 ppb | 21 ppb |
| Molybdenum | 24 ppb | 40 ppb |
| Strontium | 0.18 ppm | 1.5 ppm |
| Chromium-6 | 0.2 ppb | – |
Where it serves
Ashburn, Great Falls, Bull Run, Chantilly, South Riding, Brambleton, Sterling, Herndon, Cascades
ZIP codes the system reported serving: 20120, 20146, 20147, 20148, 20151, 20152, 20164, 20165, 20166, 20170, 20176, 22066
Nearby utilities
- Fairfax County Water Authority Herndon · 6 mi · PFAS above limit
- Town of Leesburg Leesburg · 7 mi
- Town of Purcellville Purcellville · 15 mi · PFAS above limit
- Town of Round Hill Round Hill · 17 mi · PFAS above limit
- Prince William Water – West Buckhall · 22 mi
- Arlington County Water System Arlington · 22 mi
Questions
Is Loudoun Water – Central System water safe to drink?
Loudoun Water – Central System has no health-based violations since 2016. EPA testing found no PFAS above the federal limits. Federal data can't tell you about your own pipes: lead comes from service lines and plumbing, so test your tap if your home was built before 1986. For the official word, read the utility's annual Consumer Confidence Report.
Does Loudoun Water – Central System water have PFAS?
Yes. EPA's 2023–2025 testing of Loudoun Water – Central System found 1 PFAS at least once. None of the averages were above the federal limits.
What is the lead level in Loudoun Water – Central System water?
The most recent 90th-percentile lead result for Loudoun Water – Central System is 0.5 ppb, for the monitoring period that began Jan 2024 (still in progress). The federal action level is 15 ppb, falling to 10 ppb in November 2027. The 90th percentile means 9 in 10 homes sampled were at or below this number. Individual homes can be higher.
Check these numbers yourself
Every figure on this page comes from public EPA records. You don't have to take our word for it:
- EPA's own report for VA6107350: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID VA6107350).
- EPA SDWIS download: the lead results, population and violation records we use.
- Loudoun Water – Central System's 2026 water quality report: the utility's own annual report, including contaminants EPA's national database doesn't carry (link checked Nov 14, 2026). Phone: (571) 291-7844.
- Loudoun Water – Central System website
Found something that doesn't match? Tell us and we'll check it against EPA's records. How we check our data.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.