The break was reported at 9:34 a.m. at California Street and 22nd Avenue, a fire dispatcher said.
Tony Winnicker, a spokesman for the San Francisco Public Utilities Commission, said a contractor repaving a portion of California Street struck and ruptured a 12-inch water main.
"That's a pretty big main, so for a time there was quite a lot of water in the street," Winnicker said.
A woman answering the phone at Angelina's Deli-Cafe, located at that intersection, described water "rushing down the block."
She said around 10:30 a.m. that the deli had not flooded but that a nearby pet store had.
Winnicker confirmed that Cal's Pet Supply, located at 5950 California St. was one of the businesses affected.
Most of the flooding occurred in buildings' basement levels, and owners of businesses that were damaged have been given the opportunity to file claims with the city, Winnicker said.
In order to repair the main, crews had to shut off water in the area, Winnicker said. As of about 12:30 p.m., there was no water service on California Street from 18th Avenue to 23rd Avenue.
One block of 22nd Avenue, from California Street to Lake Street, was also affected, Winnicker said.