Hydrant repairs and replacements are always scheduled ahead of time. Water would be shut off in the area of the repair/replacement and the affected residents would be notified in advance.
A water leak may be discovered on a service line, which leads from the street to the home or the main valve inside. The water can be turned off at the street, which would only affect the individual household.
Water Main Break
When a water main break occurs, it may be necessary to shut off the water in the area to make the necessary repair. Residents are usually notified ahead of time, unless it is an emergency situation. When a planned water main repair is scheduled, affected residents are notified and given ample time to plan for the water shut off.