Filters
Whole-house filter vs under-sink RO for PFAS
For drinking and cooking water, a certified point-of-use carbon filter or under-sink reverse osmosis system is the practical choice. Whole-house systems sold for sediment or chlorine do not reduce PFAS, and treating every tap in the house with PFAS-rated media is costly.
What “whole-house” means
A whole-house system is a point-of-entry (POE) treatment: it treats all water as it enters the home. A point-of-use (POU) system treats the water at one faucet or fixture. The Minnesota Department of Health describes both as options for PFAS and says POU “tends to be more economical than point-of-entry”.
The problem with common whole-house products
Most whole-house filters on the market are sediment filters, carbon filters sized for chlorine taste, iron filters or softeners. The Minnesota Department of Health says plainly that “sampling data indicate that those systems do NOT remove PFAS” when it refers to whole-house softening and iron filtration. A whole-house carbon unit can in principle adsorb PFAS, but it needs a bed designed and sized for PFAS, and the media is consumed far faster when it treats thousands of gallons for showers, laundry and irrigation. Check any specific system for a PFAS reduction claim on a certifier’s listing before assuming it works.
Why under-sink reverse osmosis is the usual answer
Reverse osmosis (RO) works at the pressure available at one tap. The Minnesota Department of Health notes RO “is more practical as a point-of-use treatment option (not at point-of-entry)”. EPA says RO systems waste about one gallon for each gallon treated; EPA WaterSense estimates at least five gallons of reject water per treated gallon for a typical unit, with WaterSense-labeled models at 2.3 gallons or less. See the pros and cons of RO.
Side by side
| Whole-house (point of entry) | Under-sink carbon or RO (point of use) | |
|---|---|---|
| Treats | All water entering the home | One tap, usually the kitchen |
| PFAS claim | Rare; verify on a certifier’s listing | Available; look for NSF/ANSI 53 or 58 PFOA/PFOS claims |
| Water waste | None for carbon; softeners use water | RO sends reject water to the drain |
| Cost to run | Larger media, replaced less often but at higher cost | Small cartridges, replaced on schedule |
| Best for | Chlorine, sediment, iron, scale | Drinking and cooking water |
What to do
- Look at your utility’s PFOA and PFOS results first (find your utility).
- If you want treatment for drinking water, choose a POU system with a PFOA/PFOS claim for the exact model (what to look for).
- Keep any existing whole-house filter or softener for the job it was bought for, but do not count it as PFAS protection.
Sources
Not medical or legal advice. This guide summarizes public documents so you can ask better questions of your utility, your health department or a certified lab. For health concerns, talk to a clinician; for compliance questions, to your state drinking water program. Pages on this site that name products may earn a commission, as disclosed on the affiliate disclosure page.