PFAS Filters — UK Buyer's Guide

PFAS (per- and polyfluoroalkyl substances) are the most chemically stable contaminants that water treatment technology must deal with. Their extreme resistance to breakdown — the very property that makes them useful industrially — means that once they enter water supplies, only highly specific removal technologies work. Activated carbon (the basis of most jug filters and standard under-sink filters) can adsorb some PFAS types, but not reliably or comprehensively. The only technology certified for PFAS removal by the NSF International water safety standard is reverse osmosis (RO).

This is a critical distinction that is frequently misunderstood. A standard Brita filter, ZeroWater filter, or granular activated carbon (GAC) filter will NOT reliably remove PFAS from tap water. Only RO, certified to NSF/ANSI 58, has been independently tested and certified to remove PFAS to below detection limits. When shopping for a PFAS filter, look for the NSF mark on the product — not just the brand's claim.

Which UK areas most need a PFAS filter?

As of March 2026, 14 UK water companies hold active DWI PFAS improvement notices: Thames Water, United Utilities, Severn Trent, Yorkshire Water, Southern Water, South West Water, Anglian Water, Affinity Water, Essex & Suffolk Water, South Staffordshire Water, Cambridge Water, Portsmouth Water, Northumbrian Water, and Welsh Water. Customers of any of these companies in an affected zone may want to consider a PFAS filter, particularly if they have infants, are pregnant, or have immunocompromised family members. Enter your postcode to check your zone's status.

How does reverse osmosis remove PFAS?

Reverse osmosis forces water through a semi-permeable membrane with pores so small (0.0001 µm) that PFAS molecules cannot pass through. The membrane rejects dissolved ions, molecules, and particles including virtually all PFAS compounds. A quality NSF/ANSI 58 certified RO system removes 95–99%+ of PFAS. The water that passes through the membrane is collected as purified drinking water; the rejected PFAS-containing water is discharged to drain.

Modern RO systems — particularly tankless under-sink designs like the Waterdrop G3 — have improved significantly in recent years. Older RO systems wasted 3–4 litres of water per litre produced (very inefficient). Modern designs achieve 2:1 or even 1.5:1 waste ratios. Countertop RO systems (like AquaTru) require no plumbing installation — ideal for renters or those who cannot install under-sink plumbing.