Learn house's cutoff switches before an emergency hits Your home is a machine, in a way, with many straightforward controls such as thermostats and light switches. But dozens more don't come with explanations, such as the kill switches and cutoff valves for heating, cooling, water and electricity. They're often difficult to locate and operate in an emergency - and that's usually when you need them. Water Main cutoffs. Most homes have a main cutoff valve near the water meter, close to the entry point of the main supply pipe. If in doubt about the source of a leak, close the main valve, and the flow will slow and then stop. Fixture cutoffs. Every fixture should have cutoffs - sometimes tucked out of the way, say, between floor joists in the basement ceiling just under the bathroom. When you find them, turn each one back and forth a few times. Some rarely used valves are difficult to move. Figure on closing a valve to the right and opening to the left. With newer, in-line valve levers, there's no confusion: In line with the pipe means the valve is open; perpendicular to the pipe means the valve is closed. Special cutoffs. Exterior faucets normally have an interior cutoff. This allows you to drain any water in the outside spigot so it won't freeze and burst the pipe. There are also cutoffs for small fixtures such as a hot-air furnace humidifier. But instead of a full-size valve, you might find a small, thin bar attached to a tiny cutoff called a needle valve. Well water. Most private wells pump to a pressurized holding tank that forces out water as you open a tap. Even when a power failure stops the pump, there will be some water under pressure. That means you need to use the main cutoff or fixture cutoffs while making repairs or improvements. Tripping the pump circuit breaker will prevent the pressure tank from refilling but won't stop the stored supply from continuing to flow. Electricity Main cutoff. The main cutoff is typically set apart at the top of the electrical panel. It normally stays engaged even when an electrical problem trips one of the many circuit breakers. But in an emergency when you're not sure where the problem is, tripping the main will cut off electricity throughout the house. Circuit cutoffs. Each circuit is protected by its own breaker, or fuse in an older building. A major appliance such as an electric stove often has one circuit and breaker to itself. But most circuits supply power to several outlets or lights, and not necessarily in logical order. That's a good reason for making a circuit map - working with a partner to pinpoint which breakers control which outlets, lamps and appliances. It can be puzzling. For example, in some homes, one receptacle in a duplex outlet is always live, while the other, intended for table lamps, is controlled by a wall switch. Emergency kill switches. Many homes have two other types of cutoffs. One is a standard wall switch but with a red cover plate, often installed at the top of cellar stairs. It cuts power to the furnace. The other type is a ground fault circuit interrupter. These quick-tripping breakers are built into outlets wherever water is used, mainly in kitchens and baths. Most versions have a test and reset button that you operate at the outlet instead of at the main panel. Heating and cooling Main cutoffs. When you need to stop a furnace or air-conditioning system, there are several options. Aside from an emergency (red-plated) cutoff, heating and cooling systems typically have a cutoff switch mounted on the electric supply line near the unit. And you always can trip the unit's circuit breaker. Whether the main fuel source is electricity, oil or gas, cutting the power will stop the system because it stops pumps, blowers, circulators and thermostats that heating and cooling systems depend on. Supply-line cutoffs. For oil systems, the supply line should have a plumbing-type valve, often installed near the oil filter canister. For gas systems, the appliance should have a cutoff valve in the supply pipe as well as a turn-off knob on the furnace gas valve. Bear in mind that there are many types of controls - even gas valves that close automatically when an earthquake occurs. So you always should check the appliance manufacturer's instructions for interrupting the fuel supply and restarting the system.