PFAS, often called "forever chemicals", are a large family of man-made chemicals that barely break down in the environment and can build up in the body. Low levels are now found in many UK rivers, groundwater and drinking water supplies. This guide explains what PFAS are, what the UK guidance says, how to find out whether they are in your water, and which types of filter reduce them.

At a glance

  • What they are: thousands of synthetic chemicals, including PFOA and PFOS, used for non-stick, waterproof and stain-resistant coatings and firefighting foam.
  • UK guideline: the Drinking Water Inspectorate (DWI) asks water companies to keep the total of 48 named PFAS below 0.1 µg/l. There is not yet a legal limit in England and Wales.
  • Private supplies: if any individual PFAS is above 0.1 µg/l, contact your local authority's Environmental Health team.
  • Treatment: reverse osmosis and specialist ion exchange PFAS filters are the most effective options at home. Boiling does not remove PFAS.

What are PFAS?

PFAS stands for per- and polyfluoroalkyl substances. They are built around carbon-fluorine bonds, among the strongest in chemistry, which is what makes them so useful in products and so persistent in the environment. There are thousands of different PFAS. The two best known are PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid). Both are now restricted internationally under the Stockholm Convention on persistent organic pollutants, but because they do not break down, they remain in soil and water long after use has stopped. Industry has moved to other PFAS, including "short-chain" types, which are also persistent and are harder for some filters to capture.

You may see this page's older name, PFOAs, used online. PFOA is one PFAS; the term PFAS covers the whole group, and it is the whole group the UK guidance now looks at.

How do PFAS get into drinking water?

  • Firefighting foam used at airfields, military sites and fire training grounds, which can soak into groundwater.
  • Industrial sites that make or use PFAS, such as chemical, textile, coating and paper plants.
  • Landfill leachate and wastewater, as PFAS from consumer products pass through sewage treatment largely unchanged.
  • Sewage sludge spread on farmland, which can carry PFAS into soil, streams and shallow groundwater.

Mains water companies check their sources and treat where needed. A private supply from a borehole, well or spring has no such checks, so if your source is near an airfield, fire training ground, landfill or industrial site, it is worth considering a test. See our guide to water contaminants for how PFAS fit alongside other common problems.

Are PFAS harmful?

Research into PFAS is ongoing and the picture is still developing. Studies have associated exposure to some PFAS, mainly PFOA and PFOS, with raised cholesterol, effects on the liver and immune system, lower birth weight and some cancers. In 2023 the International Agency for Research on Cancer classified PFOA as carcinogenic to humans and PFOS as possibly carcinogenic to humans. Because PFAS build up in the body over years, the concern is long-term exposure rather than a single glass of water.

The DWI's view is that UK drinking water remains safe to drink, and its guidance is designed to keep exposure low as a precaution. Drinking water is also only one route of exposure: food, dust and consumer products contribute too.

What the UK rules say

In England and Wales there is currently no legal maximum for PFAS in drinking water. Instead, the Drinking Water Inspectorate's PFAS guidance requires water companies to monitor their supplies and sets a guideline of 0.1 micrograms per litre (µg/l) for the sum of 48 named PFAS. Where results pass set trigger levels, companies must act, which can include blending sources, extra treatment or taking a source out of use. One microgram per litre is one part per billion, so these are extremely low concentrations that need a specialist laboratory to measure.

For private water supplies, the DWI advises that if any individual PFAS is found above 0.1 µg/l, the owner should contact their local authority's Environmental Health team for advice. Local authorities regulate private supplies under the Private Water Supplies (England) Regulations 2016.

Rules are tightening elsewhere, and the UK position is under review, so check the DWI page above for the latest guidance.

How to find out if PFAS are in your water

On mains water, start with your water company. They monitor for PFAS under the DWI guidance and can tell you about results for your area; many publish water quality information by postcode.

On a private supply, nobody else is checking for you. PFAS cannot be seen, tasted or smelled, and a standard drinking water test does not include them, so you need a specialist PFAS analysis from a laboratory. Testing makes most sense if your source is near a known or likely PFAS source. Our team can advise on whether a PFAS test is worth doing for your supply.

How to reduce PFAS in drinking water

Method How well it works on PFAS Good to know
Reverse osmosis Very effective across long-chain and short-chain PFAS Fitted under the sink for drinking and cooking water. Also reduces lead, nitrate, fluoride and other dissolved substances.
Ion exchange PFAS filter Designed specifically for PFAS, including short-chain types The IX PFAS system is tested by its manufacturer against PFOS, PFOA, PFNA, PFHpA, PFHxS, PFBS and PFDA. The media is single-use: replace it with an IX PFAS refill cartridge on schedule.
Activated carbon Reduces some long-chain PFAS such as PFOA and PFOS; less reliable for short-chain PFAS Good for chlorine taste and odour. Performance on PFAS depends on the carbon, contact time and how often the cartridge is changed.
Boiling Does not remove PFAS Boiling can slightly concentrate PFAS as water evaporates.
Water softener Not designed to remove PFAS Treats hardness and limescale only.

Whichever filter you choose, change cartridges on time. A spent PFAS or carbon cartridge stops reducing PFAS without any change you can see or taste. Browse our IX water filter range and drinking water filters, or ask our team which system suits your home.

Why choose Wrekin Water

Wrekin Water is a family run company based in Bettisfield, Shropshire. We have served more than 50,000 customers over 15 years and are rated Excellent on Trustpilot. We supply and install drinking water treatment for mains and private supplies, and if you are in North Shropshire, our engineers can install it for you. For other water quality problems, see our water contaminants guide.

Frequently asked questions

Forever chemicals is the common name for PFAS (per- and polyfluoroalkyl substances), a group of thousands of man-made chemicals used in non-stick, waterproof and stain-resistant coatings and firefighting foam. They barely break down in the environment and can build up in the body over time. PFOA and PFOS are the best known.

Not yet in England and Wales. The Drinking Water Inspectorate requires water companies to monitor for PFAS and sets a guideline of 0.1 micrograms per litre for the sum of 48 named PFAS. For private supplies, the DWI advises contacting your local authority's Environmental Health team if any individual PFAS is above 0.1 micrograms per litre.

No. Boiling does not remove PFAS and can slightly concentrate them as water evaporates. To reduce PFAS you need suitable filtration, such as reverse osmosis or an ion exchange filter designed for PFAS.

Reverse osmosis is very effective across both long-chain and short-chain PFAS. Ion exchange filters made for PFAS, such as the IX PFAS system, are also designed to capture them, including short-chain types. Activated carbon reduces some long-chain PFAS but is less reliable for short-chain types. Whatever you use, change the cartridge on time.

On mains water, ask your water company, which monitors for PFAS and can tell you about results in your area. On a borehole, well or spring, you need a specialist PFAS analysis from a laboratory, as standard drinking water tests do not include PFAS. Testing is most worthwhile if your source is near an airfield, fire training ground, landfill or industrial site.