A spokesperson says the break is in a 24-inch main near Teer Quarry - where the pipe crosses the Eno River.
Workers have isolated the break from the rest of the system by closing valves.
Officials said most customers should now see their water service return to normal or near-normal levels.
If customers note air in their internal water lines, they are encouraged to run their faucets for up to two minutes to flush their lines.
If customers in this area do not have their water service restored by 5 p.m. Tuesday, they should contact the Water Management Department's after-hours emergency line at (919) 560-4344.