A TIME BOMB IN EVERY HOME!
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One day last year, at a restaurant in El Torito, California, a water heater was launched like a rocket through the wall of the facility, landing on a rooftop almost a block away. The explosion killed one person, injured several others and completely demolished one wall of the building. Dozens of incidents of this nature occur every year.

Don't get me wrong. Water heaters are eminently safe products. Over 8 million new ones get installed every year and tens of millions of existing units quietly go about their work every day producing hot water for American homes and commercial establishments. The fact that only a few dozen serious accidents occur each year out of tens of millions of possibilities testifies to a remarkable safety record. It compares statistically with that of commercial aviation, which records tens of millions of passenger miles before anything goes wrong.

Yet, when something does go wrong, the consequences are catastrophic. This is why the airline industry and its regulators spare no expense and put safety as the top priority. It is in this spirit that I discuss the remote but potentially disastrous problems associated with water heaters.

As machinery goes, water heaters are not all that complicated. Most of the operating mechanisms of a water heater are fairly simple devices such as valves and thermostats. Design, manufacture, operating and installation principles are well understood. When an accident occurs, rarely is it the fault of a product malfunction per se. The cause almost always gets traced to human error, including lack of maintenance.

Most water heaters operate continuously for years at a time without incident. They get installed in basements, laundry rooms or other storage areas away from the living space. All of this contributes to an "out of sight, out of mind" attitude on the part of the owner. More than any other home appliance, water heaters get taken for granted, and thus neglected from an inspection and maintenance standpoint.

Yet there are components of a water heater that deteriorate over time and thereby create potential hazards. This is why you ought to have a competent professional inspect and, if necessary, service your water heater at least once a year. One good way to avoid the "out of sight, out of mind" syndrome is to have this done as part of a comprehensive service agreement covering household plumbing and heating equipment. Ask your licensed plumbing-heating contractor if he can provide this service, or else refer you to someone who can.

Perhaps the most important safety device on a water heater is its temperature and pressure (T&P) relief valve. This device, which can be seen attached to the storage tank of most models, is the last line of defense against any other malfunction that might cause a dangerous build-up of temperature and pressure inside the tank. Most water heaters that explode either lack a T & P valve or have one that malfunctions.

Many water heaters get installed by novice handymen who don't understand the function of the T & P valve and fail to install one with the unit, or they get misinstalled and fail to work properly. On occasion, T & P valves develop leaks. What frequently happens is that an inexperienced repair worker discards the leaky T & P valve and fails to install a new one, or installs it wrong, or installs an incompatible model.

An old T & P valve may stick after many years of service. This won't have any impact on the day-to-day operation of the water heater. It won't be noticed until the day it is called upon to do its job of preventing disaster. Catastrophic accidents are virtually unheard of with water heaters whose T & P valves are fully functional.

Of course, a T & P valve is not needed unless something else goes wrong. If the water supply gets cut off or restricted, or the temperature controls get turned up too high or fail, water inside can overheat and turn to steam, building up enormous pressure inside the unit. The bottom of a normal tank is relatively thin sheet steel about 18 inches in diameter. Steam build-up can create a pressure upwards of 50 pounds per square inch, which multiplies to more than six tons pushing against the bottom. Sudden release of this pressure can propel the water heater skyward like a rocket - as occurred in the El Torito restaurant.

Other explosive hazards presented by a water heater have to do with gas line connections and the proximity of flammable vapors. A professional inspection ought to include testing for gas leaks, as well as proper venting - improper venting could lead to carbon monoxide asphyxiation.

Flammable vapor explosions are not the fault of the water heater per se, but result from negligence in placing flammable substances where they can be touched off by a pilot flame or ignition spark. Highly volatile substances like gasoline should never be used indoors, period. Also beware of many common household products intended for indoor use - lighter fluid, kerosene, cleansers, oil-based paints, floor and furniture polish, disinfectants, turpentine, hair spray, adhesives, etc. - but which nonetheless are flammable to varying degrees. The substances should never be stored or used in the vicinity of a water heater.

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