Due to age and corrosion, the main gas shut-off valve in up to 10% of California homes is frozen so tight that the average homeowner cannot move it to the closed position, according to a Public Utilities Commission study.
"This situation could cause widespread loss of life in the aftermath of a large earthquake," says Les Saffil of Seismic Safety Products in Los Angeles. "Homeowners must check their gas-main valves on a regular basis to avoid the risk."
Public safety officials suggest that homeowners contact the Gas Co. to arrange a test of their gas main valve or test the valve themselves by turning it with a wrench about 45 degrees (gas flow will not be interrupted and pilots will not need to be relit by turning valve only this far).
If you cannot turn the valve, contact the Gas Co. immediately for repair. If it does work, recheck it on a semiannual basis.
Don't know where the shut-off valve is?
It is almost always on the vertical or horizontal pipe that enters the gas meter on the left-hand side. It appears as a rectangular tab about 11/4-by-3/4 inches. The valve is on and gas will flow when the tab is parallel to the pipe.
Gas will stop when the tab is turned perpendicular to the pipe.
Even if your manual shut-off works perfectly, a quake can strike when no one is home to shut off the gas or access to the valve may be obstructed by debris. Because of this, many communities require the installation of an "earthquake-activated automatic gas shut-off valve."
These valves are carefully calibrated to stop gas flow at the meter in the event of a quake large enough to cause gas pipe breakage, normally about 5.5 on the Richter scale at the valve location.
The city of Los Angeles was the first major city in the nation to implement an automatic quake-valve ordinance a few years ago.
For a list of valves approved for installation in Los Angeles, contact the Los Angeles Department of Building and Safety at (888) 524-2845 or (310) 575-8094.
Only a few approved valves provide a means of manual shut-off. Others can be manually shut off by holding a strong magnet next to the body of the valve (manual shut-off capability provides another means of gas-flow interruption if the main valve is frozen).
Most plumbing contractors can provide automatic valve installation.
Whether gas is shut off manually or automatically after a large quake, safety officials recommend that gas not be turned back on until the property is checked for leaks by the Gas Co., a licensed plumbing, heating or general contractor or public safety officer.
There were multiple fires several days after the 1994 Northridge quake because property owners did not realize gas leaks existed when they turned gas back on themselves.
Gary Abrams is a general contractor who has written about home improvement for The Times for 10 years. Comments and questions can be sent to P.O. Box 711, Thousand Oaks, CA 91319. Include a self-addressed stamped envelope or e-mail him at firstname.lastname@example.org.