It happened just after 8:30 a.m.
People are advised to avoid Collingwood and 19th streets.
The San Francisco Public Utility Commission said customers on Collingwood Street between 18th & 19th are currently without water service.
It's unknown when water service will be restored.
No sinkhole has been reported.
The water main break cracked and lifted the streets' asphalt.
The San Francisco Fire Department requested hundreds of sandbags to help prevent water from going into homes and driveways.
People driving in the area are told to expect traffic delays.