Sydney's desalination plant is likely to be switched on this weekend but it won't start producing large volumes of drinking water for at least eight months.
NSW Water Minister Don Harwin says the Kurnell plant is expected to start operating on Sunday when dam levels fall below the threshold figure of 60 per cent.
"It's very likely that tomorrow the commissioning process for the desalination plant will commence," he told reporters on Saturday.
That process will take up to three months and the plant won't reach full capacity for eight months.
At that point, it will be able to supply some 15 per cent of Sydney's water needs.
"There's no reason to be alarmed about Sydney's water because, in fact, we've still got two years' worth of water supply in our dams," Mr Harwin said when describing the plant as an "insurance policy".
He said the water produced at Kurnell would slow down the depletion of Sydney's dams and play an important role if the current drought dragged on.
Sunday will likely be the first time the plant has been turned on since the extended testing phase that occurred after it first became operational in 2010, the minister said on Saturday.
Sydney's dam storages are currently at exactly 60 per cent and should dip below that when WaterNSW updates the official figures on Sunday morning.
Once up and running the desalination plant must operate for a minimum of 14 months under the metropolitan water plan.
Sydneysiders can expect their annual water bills to increase by about $30 as a result.
