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Gas Valve May Lessen Fire Risk After Quake

January 30, 1994|GARY ABRAMS | SPECIAL TO THE TIMES; Abrams is a general contractor who writes on home improvement topics for The Times. and

Once again, Southern Californians are reminded of the seismic threat we live with each day, as the region staggers to recover from the blows of the strongest earthquake in modern history.

One of the greatest dangers in a quake is fire from ruptured gas lines. Appliance feed lines may break in a temblor, and the gas spewing into an enclosed space can quickly accumulate to a sufficient concentration to catch fire if it reaches an ignition source such as a still-burning pilot light.

For these reasons, seismic or "quake-activated," gas shut-off valves were developed. These devices are mounted into the main gas supply line for a house or building and automatically stop the flow of gas before it enters the house when substantial earth movement is sensed.

The valves are in wide use in homes, hospitals, schools, factories and even in firehouses. In Japan, another quake-prone part of the world, the valves are required by law in all buildings.

There are more than a dozen manufacturers producing valves that have been tested and approved by the Office of the State Architect of California. Each approved valve must be carefully calibrated to shut off only during a quake strong enough to cause pipe damage. (Average 5.5 on the Richter scale.)

I have installed hundreds of the valves since the 1987 Whittier quake and, in spot-checking with some customers, found that the valves apparently functioned properly in the Northridge quake, triggering in the 6.6 temblor. Some valves had been reset after the first quake and did not trip in the lesser aftershocks.

Nuisance tripping is one of the most common concerns about the valves. But when the valves are properly installed, that should not be a problem. My valve is placed in a location subject to vibration from passing vehicles and has never caused a nuisance trip.

A few questions are commonly asked about the valves, such as, "How long will it take to get the gas back on if the valve trips?" "Is the valve easy to reset?" and "Why have one if my neighbors do not; won't my house burn anyway?"

If the valve trips due to an earthquake, your house must be inspected by a gas company representative or a licensed plumber to assure that there is no pipe damage before the valve is reset.

True, it could take days or weeks after a large quake to get help, but most homeowners who have them agree that the large reduction in the risk of fire the valves afford makes the inconvenience after a quake inconsequential.

All the valves on the market can be easily reset by the homeowner should they trigger accidentally (which is a highly unlikely event when properly installed). Some designs require only a screwdriver for resetting and some need a special tool that comes with the new valve.


Regarding the question of "Why have one if neighbors do not," representatives of several valve manufacturers respond: "While it may be true that you could still lose your house to fire after a large earthquake, at least you have dramatically increased the odds of getting yourself and your family out of the house safely, as the gas explosion will not occur in your home."

The typical cost of a quake valve, with installation, is $350 to $600, depending on the size of the gas pipe on which it is installed. However, it is a one-time investment that requires no maintenance and is designed to last 25 to 50 years.

Earthquake gas valves are normally installed by licensed plumbing contractors, not the gas company. Check with your plumber about experience and recommendations regarding the make of valve he or she prefers. Make sure that the valve selected is one of the more popular makes and carries State Architect approval.

Some communities require building permits before the valve can be installed, so check with your local building and safety department before proceeding.

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