Home → Water guides → How carbon filters remove PFAS
Guide · PFAS
How carbon block filters remove PFAS — and where they fall short.
Carbon block is the PFAS stage in most whole-house and under-sink filters. It works well on some PFAS and less well on others, and it stops working on PFAS long before your water starts tasting different. Here is how it works, in plain English, with the official sources.
By the PH Water Filters installation team, Revesby Heights · Updated 21 October 2026
The short version
Five things worth knowing.
- Carbon removes PFAS by adsorption: the molecules stick to the carbon’s huge internal surface area.
- It works best on long-chain PFAS such as PFOS and PFOA, and less well on short-chain types.
- A filter’s PFAS capacity is much lower than its chlorine capacity, so it can still taste fine after it has stopped reducing PFAS.
- Whole-house systems vary a lot in real homes; reverse osmosis at the kitchen tap is the most reliable option for drinking water.
- Sydney’s tap water meets Australian guidelines, so filtration is extra protection, not a fix for unsafe water.
How it works
Adsorption: PFAS stick to the carbon.
Activated carbon is full of microscopic pores. As water passes through, PFAS molecules are drawn onto the carbon surface and held there. The US EPA lists activated carbon as one of the proven PFAS treatments, alongside reverse osmosis and ion exchange.
A carbon block is fine carbon powder compressed into a solid cartridge. Water has to work its way through the whole block, so it spends more time in contact with the carbon than in a jug filter or loose granules. More contact time means more PFAS adsorbed.
Long-chain vs short-chain
Not all PFAS behave the same way.
PFAS is a family of thousands of chemicals. Longer-chain types like PFOS and PFOA stick to carbon well; shorter-chain types such as PFBS pass through sooner. The EPA’s research found reverse osmosis handled a wider range of PFAS, including short-chain types.
In June 2025 the NHMRC updated the Australian Drinking Water Guidelines for four PFAS:
| PFAS | Australian guideline value |
|---|---|
| PFOS | 8 ng/L |
| PFHxS | 30 ng/L |
| PFOA | 200 ng/L |
| PFBS | 1,000 ng/L |
Source: NHMRC Australian Drinking Water Guidelines, PFAS fact sheet. ng/L = nanograms per litre (parts per trillion).
Capacity
Why taste is a bad guide to filter life.
Carbon fills up with PFAS much sooner than it fills up with chlorine. Matrikx’s CTO+ carbon block datasheet rates a large 20-inch block for more than 900,000 litres of chlorine reduction, but about 79,000 litres for PFAS (the two are rated at different flow rates, but the gap is large). Matrikx also states more than 95% PFAS reduction at 1,500 ng/L in its own internal testing.
In practice, your water can still smell and taste clean after the block has stopped reducing PFAS. That is why we replace cartridges on a fixed schedule — yearly for whole-house systems — rather than waiting for a change in taste.
Whole house vs kitchen tap
What real-home testing found.
A 2025 Duke University study tested 89 filters in homes. Under-sink reverse osmosis and two-stage filters reduced PFAS by 94% or more. Activated carbon filters averaged lower, and whole-house systems were the most variable — some performed well, others did not, often because cartridges had not been changed.
- For showers, laundry and every tap: a whole house water filter system with a carbon block, serviced yearly.
- For drinking and cooking water: reverse osmosis at the kitchen tap or the tankless ED600.
- Looking for a certified filter? The US EPA explains how to check PFAS certifications (NSF/ANSI 53 and 58).
Sydney context
Where Sydney’s water stands.
Sydney Water publishes its PFAS monitoring results, and NSW Health keeps an information page on PFAS and drinking water. Read our guide to whether Sydney tap water is safe for the full picture.
PFAS questions
Quick answers.
Do carbon filters remove PFAS?
Good carbon block filters reduce many PFAS, especially long-chain types such as PFOS and PFOA. They are less effective on short-chain PFAS, and their PFAS capacity runs out well before the filter stops improving taste.
Is reverse osmosis better than carbon for PFAS?
For drinking water, yes. US EPA research found reverse osmosis typically more than 90% effective across a wide range of PFAS, including short-chain types.
How often should a carbon block be replaced for PFAS?
Follow the manufacturer’s schedule, not taste. We replace whole-house cartridges yearly at the $250 service.
Whole house enquiries
Get your fixed price.
We are a mobile business based in Revesby Heights and we come to you — call and you will usually speak to the person who will do the install.
- Phone
- 0409 408 993
- [email protected]
- Hours
- Monday to Saturday, 7am – 6pm
Ready for better water?
Tell us your suburb and which tap you want filtered. You get a fixed price before anyone comes out.