For most of its life, the trusty home water heater sits quietly behind a closet door, or maybe out in the garage or down in the basement, simply doing its thing. Need some hot water to do the dishes or take a shower? The water heater, maybe the most neglected of household helpers, is on the job.

Except, of course, when something goes wrong. And when that happens, you’ll know it.

What could possibly go wrong?

Leaks. If something is going to go wrong with a water heater, it’s likely to be a slow leak or a sudden bursting of the tank, according to the Insurance Institute for Business & Home Safety (IBHS). A little water on the floor might simply be from condensation around the tank. But a lot of water or a constant stream of water coming from the tank is a red flag. It’s worth having a professional check it out. An IBHS study found that 69 percent of all water heater failures result from a leak or a full-on burst.

A water heater stores many gallons of hot water and rusts over time. The pressure inside the tank, combined with a weakened structure due to rust, could cause a leak, and the tank could actually burst. That means lots of water —30, 40, 50 or more gallons —suddenly flooding that garage or basement or whatever little room it’s hiding in.

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Scalding water. Because of a faulty or improperly set thermostat, your water heater produce water that is scalding hot (or icy cold). Most experts advise setting the temperature to around 120 degrees F. If the water is too hot or too cold and fiddling with the thermostat doesn’t fix it, call a professional.

Fires. Gas water heaters, which use a flame to heat the water, could start a fire if vapors from nearby flammable materials like cleaning fluids, paint cans and gas cans find their way to the pilot light. Be sure to store these products far away from your water heater.

Consumer Product Safety Commission (CPSC) studies have delved into fires that happen when gas water heaters sit near flammable materials. From 1994 to 1998, almost 5,000 fires in the United States were associated with gas water heaters. Almost 800 of those fires, resulting in five deaths and 130 injuries, were attributed to flammable materials around the water heaters. Water heaters have improved since then, and state and local governments have instituted more stringent codes regulating the installation of the units.

Carbon monoxide leaks. A gas water heater that has been neglected, improperly installed or poorly vented could leak carbon monoxide, which can be downright deadly. Carbon monoxide (CO) is an odorless, colorless gas produced from burning fuels.

The most obvious signs that a water heater may be leaking CO comes not from the heater but from people in the house. Headache, dizziness, weakness and upset stomach are the most common signs of CO poisoning. Vomiting and chest pain, even confusion, also can occur, according to the Centers for Disease Control. If you suspect CO poisoning, get out of the house immediately and call 911 or go directly to an emergency room.

Tankless water heaters, which heat as needed and do not store water, are powered by natural gas or propane, so they also must be vented properly to get rid of carbon monoxide. A professional can check the ventilation for you.

Explosions. An explosion is highly unlikely, but there are several documented cases of explosions happening. If the temperature and pressure (T&P) valve is constantly releasing or sticking, take that as a sign that something’s wrong. Call a professional — quickly.The Discovery Channel series “MythBusters” demonstrated what can happen when hot water and pressure combine in an enclosed metal capsule.

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How to prevent a real mess

Even the best-maintained water heaters will cause trouble eventually. They rust. Parts fail. The IBHS found the average life expectancy for a gas water heater to be just under 11 years. By the time a water heater had reached 12, about 75 percent had failed. Once a water heater gets more than 10 years old, it’s time to be extra careful.

If buying a new water heater isn’t in the immediate future, there are steps to take to sidestep disaster and keep it humming.

Maintain it. The National Board of Boiler and Pressure Vessel Inspectors points out some tasks a homeowner can undertake to keep a water heater running as it’s supposed to run, including checking that critical T&P valve.

Flush it. The Department of Energy suggests flushing a quart of water from the tank every three months to rid the tank of built-up sediment.

Inspect it. Call a professional to give the water heater a checkup, and have them replace the anode rod (used to inhibit rust in the tank) every few years.

None of this will keep water heaters from eventually giving up the ghost. It happens to the best of them. But it should keep yours relatively trusty and problem-free until signs point that it’s time to buy a new one.

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John Donovan is a freelance writer and editor based in Atlanta. His most recent work has been with NBA.com and SI.com.