PFAS in Sydney’s Blue Mountains water — the full independent guide

What happened — the timeline

The Blue Mountains PFAS situation unfolded across 2024–2026 and represents the most significant urban drinking water quality event in NSW since the 1998 Sydney Cryptosporidium incident. Here is the factual chronology:

• June 2024: Sydney Water detected PFAS in treated water at the outlet of the Cascade Water Filtration Plant, which serves the Blue Mountains including Blackheath, Leura, Katoomba, Mount Victoria and Catalina. All results were below the then-current ADWG guidelines, and NSW Health confirmed the water was safe to drink.
• July 2024: WaterNSW conducted follow-up testing of all five Blue Mountains dams. Elevated PFAS was identified in Medlow Dam.
• July 2024: Medlow Dam and Greaves Creek Dam were disconnected from the Blue Mountains water supply as a precautionary measure.
• September 2024: Water transfers from Oberon Dam commenced to supplement and dilute the Blue Mountains supply.
• October 2024: UNSW researchers reported finding 31 PFAS compounds in Sydney tap water — including 21 not previously recorded in Australian tap water — using more sensitive analytical methods. The ABC reported the findings as significant in terms of chemical variety, though concentrations remained below existing guidelines.
• December 2024: A $3.4 million emergency treatment system using granular activated carbon (GAC) and ion exchange resin was commissioned at the Cascade Water Filtration Plant. Post-installation monitoring showed decreasing PFAS in treated water.
• June 2025: NHMRC published updated ADWG values for PFAS, including much lower limits: PFOS from 70 to 8 ng/L, PFOA from 560 to 200 ng/L.
• June 2025: NSW Government confirmed all NSW public drinking water supplies — including Blue Mountains — meet the updated ADWG limits.
• March 2026: A detailed site investigation (DSI) of the Upper Blue Mountains catchment is underway, investigating two highway accident sites and the Medlow Bath RFS fire station as potential PFAS sources. Expected to take approximately 12 months.

Where did the PFAS come from?

WaterNSW’s investigation has identified several potential contamination sources in the Blue Mountains catchment:

• Historical vehicle accident sites on the Great Western Highway: Emergency services responding to accidents historically used PFOS-containing aqueous film-forming foam (AFFF) firefighting agents. Highway accident runoff enters catchment waterways.
• Medlow Bath NSW Rural Fire Service station: Fire stations used PFOS-containing AFFF foams from the 1980s until the early 2000s. Training exercises and emergency responses introduced PFAS to surrounding land and groundwater.

The investigation findings suggest contamination has been moving downstream from the upper catchment into the Medlow/Greaves Creek system over time. The likely duration of contamination is unknown but may span decades given the persistence of PFAS in the environment. This is why Medlow Dam remains disconnected — not as a temporary measure but pending confirmation of effective long-term treatment.

NSW Government has committed $80–100 million for a comprehensive upgrade of the Cascade Water Filtration Plant, expected operational by 2026–2027.

What it means for the 41,000 affected households

The most important context for Blue Mountains residents: all treated water at the Cascade plant has consistently met ADWG guideline values, including the more stringent June 2025 limits. The PFAS detected in the raw (untreated) catchment water does not arrive at your tap untreated — it passes through a now-upgraded filtration system designed specifically to reduce PFAS.

What residents in Blackheath, Leura, Katoomba and surrounding areas are reasonably asking is:

• Were we drinking elevated PFAS before June 2024 when testing began? Possibly — historical testing was not conducted at the sensitivity of current methods. This question cannot be answered retrospectively.
• Does the emergency GAC/ion exchange treatment fully resolve the issue? Current monitoring indicates it is working — PFAS levels in treated water have decreased since December 2024. The $80–100M upgrade will provide a permanent long-term solution.
• Is the water safe to drink now? NSW Health and NSW Government: yes, based on current monitoring data showing compliance with the updated June 2025 ADWG limits.

PFAS in the rest of Sydney

The Blue Mountains situation attracted the most public attention, but PFAS has also been detected at trace levels in other parts of the Sydney network. The UNSW 2024 study found 31 PFAS compounds at sampling points across Sydney, with the highest average detections at Woronora and Prospect Water Filtration Plants (dominated by PFBA, a shorter-chain PFAS compound). Prospect serves the majority of western Sydney; Woronora serves the Sutherland Shire and parts of St George.

All detections at these plants were below the updated June 2025 ADWG guideline values. However, the UNSW study’s finding that PFAS levels in some tap samples exceeded the levels found in the raw source water — suggesting PFAS is accumulating from pipe deposits or entering during distribution — raises questions that ongoing monitoring continues to investigate.

This is not a situation that warrants immediate alarm for Sydney residents outside the Blue Mountains. But it is reason to be informed, to follow Sydney Water’s published monitoring data, and — for those who prefer additional certainty — to understand which home filter technologies address PFAS effectively.

Sydney’s other notable water quality characteristic: chloramine

PFAS has dominated the conversation, but the more routine water quality issue affecting all Sydney households is chloramine disinfection. Sydney Water uses chloramine across its entire distribution network — making it one of the few Australian capital cities to do so city-wide. Chloramine produces a characteristic taste and odour that many Sydney residents notice and attribute to “chemicals in the water.”

The filtration implication: standard GAC carbon filters — including most pitcher filters sold in Australia — have limited effectiveness against chloramine. Sydney households wanting to address chloramine taste need either catalytic carbon or a multi-stage under-sink filter with sufficient contact time. This is the same issue as Melbourne’s western suburbs, but city-wide across Sydney.

What removes PFAS — the Sydney-specific picture

For Blue Mountains residents specifically concerned about PFAS, or for any Sydney household wanting the most comprehensive protection, NSF 58-certified RO is the clearest recommendation. For broader Sydney residents primarily concerned about chloramine taste and wanting PFAS reduction as a secondary benefit, a quality catalytic carbon block under-sink system with a specific PFAS certification claim is a practical and significantly cheaper option.

For shorter-chain PFAS compounds (like PFBA, which the UNSW study found at Prospect and Woronora), RO is more effective than carbon adsorption — shorter-chain PFAS molecules are less strongly adsorbed by carbon media.