Typically, the water shut-off valve is in the basement or an exterior wall, depending on the geographical location of the home. The location of the water valve is dependant on the climate conditions in the area. Though all homes have a water shut-off valve, it is mainly a manual valve. However, if an automatic shut-off system is installed, it is typically located in the same area as a traditional manual water valve.
To figure out the location of the water shut-off valve, be aware that main shut-off valves are located inside in areas where climates reach cooler temperatures. This includes the basement area or any area that tends to stay warm to prevent freezing of the water line. In warmer climates, valves are typically connected to an outside wall or in an underground container with a lid. The shut-off valve looks like a round handle with notches that require several rotations to turn it off. In recent homes, the valve could be a ball valve, which is a valve with a lever that must be pulled to turn it off.
If there are water sensors connected to the water shut-off valves, this means an automatic water shut-off system is installed in the home. An automatic system detects water leaks and automatically turns off the water source. The valves are not limited to the main supply valve, but to the fixture supply stops as well, which are localized valves that are installed on supply lines for things such as toilets, dishwashers and washing machines. It is possible to distinguish these supply stops by an oval or round handle that a person can turn to shut off localized water flow.