Towns and localities affected are Quaama, Cobargo, Bermagui, Beauty Point, Fairhaven, Wallaga Lake, Wallaga Lake Heights, Wallaga Lake Koori Village and Akolele, as well as trunk main customers in these areas.

All water for drinking, food preparation, the cleaning of teeth and ice-making should be boiled before use.

Boiled water can be cooled and stored in a clean container with a lid and refrigerated.

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Council's water and sewerage services manager, Chris Best said the temporary treatment facility in Brogo is currently unable to keep up with increased demand.

"Our water treatment team have been working around the clock since heavy rain fell on the catchment last Thursday," Mr Best said.

"However, with more visitors in the area over the summer break, it has reached the point where the treatment plant can no longer cope with the higher demand.

"The temporary plant has reduced the need for boil water notices since introducing flocculation technology this year, but even this has its limits which is why we are in the process of constructing a permanent treatment and filtration plant at the same site.

"When commissioned late 2022, it will end the need for Brogo-Bermagui connected customers to boil their water after heavy rain.

"We have previously avoided boil water notices by carting water from our southern supply, however given the increase in usage at this time of year this is currently not possible.

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"Our water team will continue with a regular program of testing water from the Brogo River source, which is known for high turbidity levels, particularly following the Black Summer bushfires which heavily impacted the catchment."

Council will advise residents through local media, council's website and Facebook page when the boil water notice is lifted.

Water supplies in all other areas of the Bega Valley Shire are currently unaffected.