Water should be boiled for one minute before it is consumed.
''This includes any water that will be consumed, such as water to brush your teeth, food preparation and washing food that will not be cooked.''
He said the large volume of rain in other areas had made the Pomahaka River extremely dirty where the water for the schemes is extracted from.
There was a risk of bacteriological contamination.
Mr Witt said the supply was being monitored and further testing will be carried out over the next few days.
The boil water notice is in effect until further notice.
Mr Witt advised customers to check their property for overflowing troughs and leaks.
He asked that they be fixed promptly.
''Please also be vigilant for any leaks on water scheme pipelines.''
He asked residents to contact the Clutha District Council if they saw any leaks.