The Uniform Plumbing Code (UPC) instructs that hot water heaters in garages need to be placed 18 inches off the floor. The idea: keep vehicles from crushing the tank, and keep potential ignition sources (both gas and electric) away from the floor, where flammable fumes from gasoline and other solvents tend to collect.
In the past year, concerns about the safety of water heaters in garages—especially gas powered ones, have become more intense, due in part to efforts of the U.S. Consumer Product Safety Commission (CPSC), based in Washington, to spread the word.
One recent report notes that “gas water heater ignition (no mention of electric heaters, though those too are listed in the UPC requirements) is involved each year in nearly 800 residential fires, resulting in about five deaths and 130 injuries annually.”
Some building jurisdictions now require the placement of a steel post or “bollard” in front of the heater as additional protection. This makes sense, considering the proliferation of large vehicles such as SUVs. Their bumper height may exceed the 18-inch mandate.
You may also have some help on the way from the Gas Appliance Manufacturers Association. It has called for adoption by manufacturers of a voluntary safety feature for residential gas hot water tanks. This flame arrestor technology is supposed to prevent flashback by isolating and burning dangerous vapor spills inside the heater itself, rather than igniting the whole room. In addition, the CPSC reports that makers of gasoline cans now offer “spill-proof” and child-resistant features.