People turn off the flow of water from a main line to secondary pipes throughout a house when dealing with various situations. Sometimes the situation involves a natural disaster such as a winter freeze or earthquake, or human actions such as construction or underground drilling, that result in a damaged, leaky or broken pipe. Other situations include installation of a new appliance that relies on water, such as a whole house dehumidifier or sprinkler system or vacation preparation.
Shut off any appliances in the house that relies on a continuous flow of water such as a boiler, hot water heater or whole-house humidifier. Follow any shutdown instructions provided in the owner's manual for each appliance.