The Water Damage an Earthquake Causes (And How To Reduce It)

Water heaters. A full tank weighs several hundred pounds and stands on a narrow base. Unrestrained, it walks or topples, and when it does it takes its rigid supply and gas connections with it. This is the single most common post-quake water source in California homes, and it's also the cheapest to prevent.

Rigid connectors. Anywhere plumbing transitions to an appliance with hard pipe rather than a flexible connector, differential movement shears the joint. Heaters, washing machines, dishwashers, refrigerator lines.

Fire sprinkler systems. In multi-family and commercial buildings, sprinkler piping is rigid and its supports are designed primarily for gravity load. Lateral movement shears heads and cracks piping, and a single sheared head discharges continuously until the system is isolated.

Supply lines inside walls. Older galvanized, already brittle from internal corrosion, cracks at threaded joints. These leaks are hidden and can run for a long time — particularly if the property is unoccupied after an event.

Drain and waste lines. Cast iron is brittle and fractures at joints and hubs, producing the slow contaminated seep described in our guide to cast iron drain pipe failure.

Strap the water heater properly. California requires seismic strapping, and a great many installations are inadequate — one strap, or plumber's tape, or straps not anchored into studs. The standard is two straps, upper and lower thirds of the tank, anchored to structure, with the tank blocked from rocking. It's an hour's work and it prevents the most likely single source.

Flexible connectors everywhere. Corrugated stainless flex connectors on the heater's water and gas connections, braided stainless on the washing machine, flexible supply lines at every fixture. These absorb differential movement instead of transmitting it into a rigid joint. Inexpensive, and they're the difference between a wobble and a rupture.

An automatic shut-off. This is the highest-value item because it works when nobody is home. A seismic gas shut-off valve closes the gas supply on shaking — genuinely important for fire risk. A water leak sensor with a motorised valve on the main closes the water when it detects flow patterns or moisture. Some smart water monitors also close on seismic trigger.

The whole package costs less than the deductible on most policies.

Worth doing while you're at it:

Once you've confirmed people are safe and the structure is sound enough to be in:

Check the water heater first — is it upright, are its connections intact, is there water in the pan? Then the laundry, under sinks, and around the dishwasher and refrigerator.

Listen. With everything off, a hissing or running sound means a pressurised line is losing water inside the structure. Shut the main.

Look at your water meter with all fixtures off. Movement on the low-flow indicator means water is leaving the system somewhere.

Check ceilings and the base of walls on every floor over the following days. In-wall failures from a quake often surface slowly.

If you smell gas, leave and call the utility from outside. Don't switch anything on or off.

And if the property was unoccupied during the event — a second home, a rental between tenants, a business closed for the weekend — treat the inspection as urgent. Unattended post-quake leaks are how a minor pipe failure becomes a total loss.

This is the part worth understanding before you need it. Standard California homeowners policies exclude earthquake damage. That exclusion is broad and it extends to damage caused by the earthquake, including water damage from plumbing that failed because of shaking.

So the intuitive assumption — "the pipe burst, burst pipes are covered" — frequently doesn't hold if the cause was seismic. Earthquake coverage is a separate policy, typically through the California Earthquake Authority or a private carrier, with its own deductible structure that is usually a percentage of the dwelling limit rather than a flat sum.

There is nuance. Some policies treat fire following an earthquake differently, and the precise wording around resulting water damage varies between carriers. It's genuinely worth reading your own policy language on this rather than assuming either way.

The practical takeaway: the preventive fittings above are more valuable in the seismic scenario than in any other, because the insurance backstop you're used to may not be there.

Los Angeles has the housing stock this hits hardest. A very large share of our service area is pre-1980 construction with original galvanized supply and cast iron waste plumbing — materials that are brittle and already compromised internally.

Sylmar and the north Valley have direct experience of this. Northridge gave its name to the event that produced the soft-story retrofit ordinance, and buildings across Koreatown, Westlake, Hollywood and Van Nuys are working through that programme now — which, as covered in our article on retrofits and the damage they uncover, is also the best opportunity to address the plumbing.

For a homeowner, none of that is abstract. Two straps, a handful of flex connectors and an automatic shut-off is an afternoon and a modest amount of money against the most likely form of damage you'll actually experience.