A water main break in San Francisco’s Bayview District damaged at least seven homes early Friday, officials said. The 12-inch main broke around midnight at Key Avenue and Keith Street, causing a river of water to flow down the street and flooding the lower units or garages of homes on Carr Street, said Tyrone Jue, a spokesman for the San Francisco Public Utilities Commission. Workers turned off the water around 4 a.m., he said. Homes on three blocks remained without water service after 7 a.m.