It's a common scenario: your insurer flags a requirement for a seismic gas shutoff device, a contractor quotes you a mechanical ball-and-cup valve, and you assume the requirement is met. It may be. But there are questions worth asking before you sign off — because a mechanical shutoff valve and an electronic earthquake trigger recorder are not interchangeable.

What a mechanical seismic valve actually does

A mechanical shutoff valve — sometimes called a California valve — sits in-line on your gas supply pipe. A steel ball rests on a tapered cup. When horizontal shaking exceeds the threshold the valve was built to, the ball displaces and closes the valve. No power required, no electronics, no configuration.

It shuts off gas at one point in the supply. That is all it does. It does not record that an event occurred, it cannot trigger other systems, and it offers no adjustable sensitivity. Once activated, it requires manual reset before gas can be restored.

What an electronic earthquake trigger recorder adds

An electronic earthquake trigger recorder — such as the Solid State Seismic Shutoff — MK6 — detects ground acceleration electronically and fires an output relay within 10 milliseconds of exceeding the set threshold. That relay can close a motorised gas isolation valve, but it can also trigger fire alarms, isolate industrial equipment, shut down HVAC systems, or signal a building management system.

It also records every activation. After an event, you have a factual log showing whether threshold shaking occurred — useful for compliance records, insurance claims, and post-event building assessments.

Five sensitivity settings let you calibrate the device to your specific location and building type. The relay holds for eight seconds after the last exceedance, maintaining isolation through aftershock sequences.

Questions to ask your insurer before purchasing

Policy wording varies. Before assuming a mechanical valve satisfies your requirement, ask your insurer or broker these specific questions:

• Does the policy specify the type of device? "Seismic shutoff valve" typically means mechanical. "Seismic gas isolation device" or "automatic earthquake shutoff" may include electronic triggers — confirm which is intended.
• Is event recording required? Some insurers or risk assessors require documented evidence that a shutoff occurred. A mechanical valve provides none. An electronic recorder does.
• Does the requirement cover the main supply only, or all gas-connected equipment? A single mechanical valve on the main supply won't isolate individual gas appliances or equipment on separate branches. If your building has multiple gas zones, a multi-output electronic trigger may be the only practical solution.
• Is a specific sensitivity threshold specified? Mechanical valves are factory-set. Electronic triggers are field-adjustable. If your insurer or engineer specifies a particular g-level, check whether the mechanical valve on offer actually meets it.
• Does your building have other systems that need to respond to a seismic event? If gas shutoff needs to also trigger a fire alarm panel or isolate plant, a mechanical valve cannot do this. An electronic trigger with relay output can.

When a mechanical valve is sufficient — and when it isn't

A mechanical valve is a reasonable solution for a simple installation: a single-tenancy retail or office premises with one gas meter, no plant room, no downstream equipment requiring independent isolation, and no insurer requirement for event logging. In that scenario it is low-cost, low-maintenance, and meets the minimum.

It stops being sufficient when the building is more complex. A commercial kitchen with multiple gas appliances on separate branches, a multi-tenancy building with individual meters, or any site where gas shutoff needs to also trigger fire alarms or isolate plant — none of these are well-served by a single mechanical valve on the main supply. The same applies if your insurer or risk engineer has asked for an event log: a mechanical valve cannot produce one.

In many commercial buildings, both devices are installed together — the mechanical valve as a passive fail-safe on the main supply, the electronic recorder as the active, connected, auditable layer that handles everything else. They are complementary, not alternatives.

If you're not certain what your insurer's requirement actually covers, get in touch — we can help you understand the specification and confirm whether the MK6 meets it. See also the compliance page for relevant NZ and Australian standards.