The water service was restored at 12:15 p.m., Marin Municipal Water District spokeswoman Libby Pischel said.
The break occurred on Eliseo Drive and Via La Cumbre near the Greenbrae border. The Kentfield Fire Protection District responded around 2:15 a.m., fire Capt. Dave Glenn said.
The California Highway Patrol was at the scene when the fire department arrived, Glenn said.
Water from the ruptured main caused an 18- to 20-foot stretch of one lane of Eliseo Drive to rise about 6 inches, Glenn said.
The water district was informed of the break in the underground 4-inch cast-iron pipe at 3:22 a.m., district spokeswoman Libby Pischel said.
The estimated flow was 2,200 gallons per minute, and the water was shut off at 3:46 a.m., she said.
With that flow, about 200,000 gallons of water would have spilled from the main between 2:15 a.m. and 3:46 a.m.
Thirteen homes initially lost water service, and the district cut off water to 20 additional homes this morning in order to access the water main and repair it sooner, Pischel said.
The cause of the rupture is unknown, but the water main was installed in 1952 and a valve may have broken, Pischel said.
