The Merced Public Works Department says the main broke on G Street near Bear Creek Drive early Friday morning.
The break also damaged part of the roadway. The initial repair work was expected to last all day Friday, but now officials say the work will take a couple of weeks.
Crews say the closure will be in effect on G Street from Bear Creek Drive to Park Avenue.
Officials said a church had lost water, but all other nearby businesses still had access.
Anyone who travels through the area is advised of possible delays. Authorities are asking drivers to detour at Olive Avenue or to use M and R Streets.