A family leaves for a long winter vacation and, because they don't know where the water valve is or what it's for, they come home to $40,000 in flood damage.

A washing machine hose comes loose and, because the water shut-off valve has rusted after two decades of disuse, the leak turns into a major flood.

"We run into it all the time," said Arron Lanphear, a professional handyman in Middleton.

The fact is, a lot of people don't know their homes as well as they should.

Consider this an introduction. We've asked local experts to identify a few basic systems in the typical house or apartment that you should find, maintain and learn how to use.

Use the list as a winter safety checklist, a pop quiz or the basis for a scavenger hunt. In the end, you may find yourself better prepared for any emergency this winter brings.

Water works

The scenario: Water is gushing from burst pipes. A washing machine hose comes loose and water is flooding the basement. The dishwasher sends water pouring into the kitchen. A faucet won't turn off.

The fix: The water shut-off valve. This valve controls the flow of water from your well or the public water supply into all faucets, toilets, showers, tubs and washing machines in your home.

Where to look: If you have public water, the valve is next to the water meter. Usually the meter is in the basement, often on the street side of the house. If you have a well, look for the valve on the house side of the pressure tank.

How to use it: Twist the valve until the water stops. (If you have a well, cut power to the pressure tank, too, so the pump doesn't burn out). You can also control the water by shutting the valve on the appliance itself. Toilets, sinks, dishwashers, washing machines and hot-water heaters usually have local valves that can be shut off.

Tips: Test all the water valves in your house, especially the main one. Old water valves tend to rust and freeze up if you don't turn them once in a while. Professional handyman Arron Lanphear recommends giving all the water valves in your house a twist once a year. If your valves won't close easily or look rusted, don't force them. Call a plumber.

Also, it's a good idea to turn off the water at the main valve and drain the faucets before you leave the house for a long winter vacation, Lanphear said. That way you won't come home to burst pipes and a flood.

Power's out

The scenario: You set the toaster, pop something in the microwave and flip on the garbage disposal, then the power cuts out. You've overloaded a circuit.

The fix: You need to find the electrical panel, which controls the flow of power from outside your house to all the electrical circuits inside the house.

Where to look: The circuit breaker (or fuse box in older homes) is usually in the basement of a house and on the wall of an apartment (check the kitchen or hallway).

How to use it: To get the power flowing again, open the electrical panel. If you have a fuse box, replace the fuse that's broken (you may actually see the break or a darkened fuse, or you can find it using a diagram of the box or trial and error). If you have a circuit breaker, look for the lever that's a little bit out of line with the rest. Flip it to the off position and then flip it on again.

Tips: Ever wonder what that "test" and "reset" buttons are for on the bathroom power outlet? It's not just an extra step to keep your blow dryer working. It's a way for you to make sure this outlet's safety feature - cutting power to prevent electrocution - is working. The U.S. Department of Energy recommends monthly testing this type of outlet, known as a ground-fault circuit interrupter. To test, plug in a night light or a lamp and turn it on. Press the test button. The light should go off. Press reset and it should come back on. If the light does not go off, call an electrician.

Fighting fire

The scenario: Your dish towel catches fire when you accidentally let it dangle over a hot stove. Luckily, you remember you have a fire extinguisher that's been sitting in a pantry closet for 10 years. You pull the pin, squeeze the trigger and nothing happens.

The fix: Check the gauge on your fire extinguisher periodically to make sure it's still charged. Home fire extinguishers lose their propellant over time.

Where to look: Keep a fire extinguisher in the kitchen and anywhere else a fire might start, such as a basement workshop, said Capt. Michael Buote, who runs fire prevention and education for the Methuen Fire Department. Store it near an exit so you don't trap yourself in the building if the fire gets out of hand.

How to use it: Aim at the base of the fire and sweep side to side until it's extinguished. You don't want a really big fire extinguisher for home use, Buote said, because if the fire's large, you shouldn't try to fight it yourself. You should get out of the building as quickly as possible.

Tips: Change the batteries in your smoke detectors twice a year. If the old batteries still have life in them, use them for something else, Buote said.

Also, as you get ready for winter, don't bring gasoline cans, propane tanks from grills, lawn mowers, motorcycles or anything else containing combustible fuel into the house for storage. They should all be kept outside in a garage or in a shed. The gasoline or propane fumes could build up in an enclosed indoor space in your home and ignite.

Goodbye to septic woes

The scenario: Black sewage backs up into your home's toilets and drains. The grass over your septic system leach field is disturbingly green. Perhaps you see sewage flowing on the ground over the septic system.

The fix: Garbage disposals are the worst offenders when it comes to causing septic system problems because they dump raw materials directly into the tank, where they take a long time to break down. A septic tank needs to be double the normal size to handle a garbage disposal, said Ray Dionne, general manager of Felix Septic Service in Southern New Hampshire. Another common septic system culprit is a water softener that may have been set up to empty into the septic tank.

Where to look: To find the source of the problem, follow the line that leaves the water softener. If it ends in the septic system rather than in a dry well of its own, you could have a problem. The salt collected by the softener kills the bacteria that are the engine of a good septic system, and the minerals can clog the leach field.

How to use it: A typical household with a few children should have its septic tank pumped once every few years, Dionne said. A newer septic system may have a filter that needs to be changed regularly, too. Avoid dumping huge amounts of bleach down the drain (a little bit is fine) and avoid antibacterial soaps, he said. Both can disrupt the bacteria powering the septic system. Avoid powdered soaps, which can clog the lines.

Tips: There are a lot of products on the market that claim to protect your septic system but don't work, so save your money, Dionne said. You don't need a special septic-safe toilet paper, he said. Any kind of toilet paper is fine. And in his experience, expensive additives don't do much, either.

Hot and steamy

The scenario: The hot water in your sink gets so hot it steams and you can't hold your fingers under it. Your shower is hotter than you like and you don't want to pay to heat the water hotter than you need. Or perhaps the water never gets warm enough and you'd like a good hot shower for a change.

The fix: Adjust the thermostat on your hot-water heater.

Where to look: First locate the water heater (try the basement). Most electric water heaters have a little dial that can be turned to change the temperature.

How to use it: Adjust the dial just a tiny bit, Lanphear said, and wait a couple of showers to see if you notice a difference. Turn it further, in small increments with plenty of showers in between, if necessary.

Tips: For each 10 degrees you lower the water heater temperature, you save 3 to 5 percent on energy costs, according to the U.S. Department of Energy.