The advisory affects approximately 260 properties.
This includes homes along Brigadoon Drive, Apple Blossom Drive to Glenview Place, Matthew Street, Nature Court, Gledhill Crescent, Galt Street, Glenview Place, and Graywood Road.
Hamilton Water is in the process of contacting residents and distributing yellow coloured Boil Water Advisories door-to-door.
The city says lab test results indicate excessive bacterial contamination in a water sample collected from a fire hydrant on Brigadoon Drive on September 19th.
Further sampling will take place over the next 24 to 48 hours to verify the safety of the drinking water.
Residents are being advised to use an alternate supply or boil water for one minute before use.
If new samples are found to be bacteria free, the city anticipates that the advisory will be lifted by Friday.