PFAS in tap water: what the numbers mean and what removes it
PFAS are man-made chemicals that do not break down in the environment. EPA finalized the first enforceable drinking water limits for PFOA and PFOS in 2024. Utilities on the Potomac have reported low-level detections in monitoring, and the practical fix at home is reverse osmosis.
Signs you have it
- No taste, smell or color; PFAS can only be found by lab testing
- Utility report lists PFOA, PFOS or "PFAS" detections
- Home near an airport, military base, firefighting training site or industrial area
What causes it
PFAS come from firefighting foam, non-stick coatings, stain repellents and industrial processes. They reach rivers and groundwater and pass through conventional treatment plants because they are extremely stable.
In the DMV specifically
Fairfax Water, Loudoun Water, WSSC and the Washington Aqueduct all draw from the Potomac and publish PFAS monitoring results. Detections in the region have generally been low, but EPA's limit for PFOA and PFOS is 4 parts per trillion, which is very low. Private wells are not monitored at all.
What fixes it
Recommended
Reverse osmosis at the kitchen sink
Membranes certified to NSF/ANSI 58 for PFOA and PFOS reduction remove the large majority. EPA names RO as one of the two effective home treatments.
Also useful
Activated carbon (partial)
Granular carbon adsorbs PFAS but needs long contact time and frequent replacement. It is a useful pre-stage, not a standalone answer at whole-house flow.
Also useful
Lab test if you are on a well
A PFAS panel costs a few hundred dollars and is the only way to know. We include it on request with any well assessment.
What does not work
- Boiling (concentrates PFAS)
- Water softeners (no effect on PFAS)
- Most pitcher filters unless specifically certified for PFAS
Related questions
Should I be worried about PFAS in Fairfax or DC water?
Utilities in the region publish their monitoring results and have reported low levels. If you want certainty at the tap, an NSF/ANSI 58 certified reverse osmosis system removes PFAS along with lead and dissolved solids for a few hundred dollars.
Does the whole-home system remove PFAS?
No, and we will not tell you it does. PFAS removal for drinking water is the reverse osmosis unit's job, which is why our standard package includes one.