Earthquake gas shut-off valves — how they work and why San Jose homes install them

Why San Jose homes need one

Post-earthquake fires — not the shaking itself — cause a large share of building losses in major California quakes. When a shaking event ruptures a gas line inside a wall or under a slab, gas flows until someone finds and closes the meter valve. A seismic shut-off valve closes that window automatically, in the first seconds of shaking, without anyone needing to be home.

How the valve works

• A metal ball sits above a seat inside the valve body
• Sustained ground motion above the design threshold (calibrated to roughly a 5.4 magnitude event) shakes the ball off its perch
• The ball drops into the seat and blocks gas flow
• Gas stays off until a person manually resets it

No power, no sensor, no wireless signal. This is exactly what you want in a safety device that has to work in the middle of a major event.

Where it's installed

Two common locations:

• Meter-side (utility-installed): PG&E can install a valve on their side of the meter in some cases
• House-side (plumber-installed): A licensed plumber installs the valve on the customer-owned line, downstream of the meter — the most common option

California code — the short version

California SB 1637 requires an automatic seismic gas shut-off valve on many properties at the point of a substantial addition, alteration, or repair (over a set dollar threshold). Some local jurisdictions require them earlier. Many insurance carriers offer a small premium reduction after installation. We check the applicable requirement for your address before we quote.

What a proper installation includes

• Verify the correct valve size for your meter and load
• Install upstream of any branches so the whole home is protected
• Support the piping and valve per code
• Pressure test the line after cut-in
• Pull the permit and schedule the inspection
• Show you where the reset is and how to use it

After an earthquake — what to do if the valve tripped

1. Check for the smell of gas anywhere in or around the home before doing anything else
2. If you smell gas, leave the property and call PG&E or 911 from outside — do not reset the valve
3. If there's no smell and no visible damage to gas appliances or lines, you can reset the valve at the valve body
4. Relight pilots on gas appliances that require it, or have a plumber do it
5. If you're unsure at any step, call a licensed plumber before restoring gas

Related

See also our guide on what to do if you smell gas and our gas line repair service page.