Up to 40,000 residents on the NSW Central Coast were told to boil drinking water, after E. coli was previously detected in a reservoir, but new testing has cleared the supply of contamination.

Flood-affected New South Wales residents are reminded to stay vigilant with flooding still isolating communities in the Hunter and Central Coast.

Central Coast residents and businesses are advised: To bring to a rolling boil any water used for drinking or food preparation. Kettles with automatic shut-off switches can do this.