The break and necessary pavement repairs caused road and freeway ramp closures Sunday and Monday.
Emergency personnel were dispatched at about 2:15 p.m to Las Positas Road and Calle Real, where the main break was causing the roadway pavement to buckle, fire Battalion Chief Robert Mercado said.
Traffic was shut down on both streets, as well as the Highway 101 overpass, and motorists were being detoured around the problem, Mercado told Noozhawk.
The freeway exit ramps at Las Positas Road were closed for pavement repairs and the city said they were expected to reopen by 4 p.m. Monday.
More repairs will be done Wednesday in the area of Calle Real and Las Positas Road, according to the city.
Water service was restored around 10:30 p.m. Sunday.