Most of us don't think about our water heater as long as we get hot water when we need it. Home inspectors often find significant safety problems with gas-fired water heaters. An improperly installed water heater can spill toxic fumes, start a fire, or damage your home by leaking water.

A gas-fired water heater located in a garage, or in a room that shares the garage floor, should be elevated on a sturdy platform so the flame is at least 18 inches above the floor. Gasoline fumes are heavier than air and will collect near the floor, where they could be ignited if the water heater flame is close to the floor. The water heater should be rigidly secured in place with special heavy-duty straps or braces to keep it from moving in an earthquake. Flexible water supply and gas supply connectors should be used, as they are less likely to break in an earthquake. The water in the tank may be the only supply of water if the water pipes in the street break during an earthquake.

All water heaters should be equipped with temperature and pressure relief valves (TPR) to prevent a malfunctioning water heater from overheating and exploding. You should find the TPR valve at the top or on the side of the water heater. This valve should have a drainpipe that extends to the exterior of the building, though some jurisdictions allow this pipe to drain on the garage floor. TPR valve leakage is common and the discharge pipe should terminate where you will easily notice any drips or water flow at the pipe, indicating a leaky valve. Leaking TPR valves should be replaced.

Fumes from gas-fired water heaters must be carried safely outdoors by a vent piping system. The bottom portion of this vent, called the draft diverter, is typically located at the top of the water heater. The diverter and vent piping can get very hot and it's very important to avoid storing any items on or near the water heater. The best systems use double wall "Type B" vents that extend through the roof. Type B vents require one-inch clearance to combustibles and single wall vent pipes need at least six inches clearance. We often find hot vent pipes located too close to discolored or charred wood, which can easily catch fire.

Flue gas spillage indicates an obstructed or improperly installed vent. Moisture is a byproduct of natural gas production and will often cause rusting at the piping near the draft diverter on top of the water heater or at the firebox opening at the bottom. Flue gas spillage is a hazardous condition and you should call your plumber or the local utility company if you suspect this condition. Installing carbon monoxide detectors near all gas-fired appliances is a good safety measure.

Gas-fired water heaters require a source of fresh air to provide oxygen to the flame. A water heater in a closet, or a confined space such as a laundry room, requires ducts or openings to the outside to assure an adequate air supply. Exhaust fans in laundry rooms can also cause flue gas spillage and an insufficient supply of oxygen can cause the water heater to produce carbon monoxide.

Almost all water heaters eventually fail and leak. Water flowing from a leaky water heater can cause substantial damage, especially if it happens while you are away for a few days. New water heaters are usually required to have a catch pan and drain beneath them when installed in areas where leakage could cause damage.

Be sure the water from your heater is not so hot that it could scald you, a child, or anyone unable to move quickly out of the way. The preferred temperature is 120 degrees Fahrenheit. Most of us don't think about our water heater until it stops producing hot water when we need it. Why don't you take a look at your water heater now and do a safety check of your own. You may be glad you did.