Scottish Water is now working to identify the issue across Eyemouth.
The fault has been located on Toll Bridge Road, and may cause some traffic disruption while the water company carries out repairs.
Meanwhile, Eyemouth Primary School has closed to pupils while action is taken to resolve the issue.
East Berwickshire councillor James Anderson posted a message to townsfolk, saying: “Please be patient with Scottish Water staff who will be working hard to repair the problem and get our water supply back on.”
He added: “The main pipe has got a fault on it. It happened a few years ago when it burst with the pressure in it.
“It’s probably going to be a long day with no water. It seems to be affecting the south side of the town, the Deanhead area seems to be unaffected, which is on the new supply.
“The Avenue and the centre seems to be off aswell. The company has a time by which they have to get it reconnected, before they start sending out the bottled water. Hopefully it will be fixed by tea-time.”
Customers can sign up for alerts at https://customer.scottishwater.co.uk/alerts/