The Guardian reported that record-breaking high tides have caused disruption along the California coast, with seawater moving into low-lying communities from San Diego to the San Francisco Bay Area. According to the report's summary, the surge is "submerging streets, homes and businesses." The article is by Gabrielle Canon in San Francisco, and it is available at The Guardian's coverage of the California high tides.
The summary does not describe water supply systems, private wells, or household plumbing. What follows is a general inspection order for any property where seawater has reached the ground floor or the equipment area, not a finding about any specific home or utility.
Why seawater is a different problem from rainwater
Floodwater from rain carries sediment, organic matter, and microbial load. Seawater adds a large dissolved salt load, mostly sodium and chloride, which shows up as high total dissolved solids and conductivity. Standard sediment and carbon cartridges do not remove dissolved salts. A water softener can be overloaded by high sodium, and a reverse osmosis membrane is designed for feed water within a defined salinity range. Brackish or saline intrusion can exceed that range, and fouling from silt can shorten membrane life even when the salt load is lower.
The practical consequence is that a home system that appears to run normally may still be delivering water that has not been characterized. Pressure and flow tell you about the equipment, not about the water.
Start with power and the source
Before anyone opens a cabinet or touches a pump panel, confirm that electrical components are not submerged or wet. If they are, shut off power at the source and have a licensed electrician assess the equipment. Water and live circuits are a hazard that outranks any water-quality question.
For a private well, check the wellhead. A cap, vent, or casing top that sits below flood level gives surface water a direct route toward the aquifer. Look for cracked seals, displaced caps, and sediment in pits or vaults. Note what you find with dated photographs before anything is cleaned or repaired, because the condition record is what an inspector, lab, or insurer will ask for.
For a municipal connection, the question is different. Ask the utility whether it issued any notice about pressure changes, main work, or service interruptions in the affected area. That answer tells you whether the building's supply path was disturbed, even if the source water itself was not.
Sample before you assume the water is safe
Testing is the step that turns suspicion into a record. For a private well, a certified laboratory can run total coliform and E. coli analysis, along with chloride or conductivity, which indicates the salt load. Follow the guidance of your state or local health authority on disinfection and on when water is safe to use, and do not treat untested water as potable because the tap still flows. The lab will need the sample collection method, date, and location recorded on its chain-of-custody form.
For a municipal supply, the utility's own monitoring is the starting point, but a homeowner can still request a sample from the tap if the building's internal plumbing was flooded or if a backflow device sits in the affected area.
Equipment that was under water
Treat cartridges, filters, and membranes that were submerged as spent, regardless of how they look after cleaning. A softener's resin bed, a reverse osmosis membrane, and a pressure tank's bladder each need a specific assessment from the manufacturer or a qualified service provider. Water heaters, tankless units, and pumps that sat in standing water may have damaged controls or corroded fittings, and a unit that powers on has not been verified as sound.
Keep every invoice, part list, and inspection note. Warranty claims and insurance reviews usually depend on proof of the event date and the equipment's condition before repair. If you are reviewing what your household coverage includes for these systems and appliances before a failure, read the exclusions for flood and water damage, since many policies treat them differently from ordinary breakdowns.
A workable order
Confirm electrical safety first. Document the source and the wellhead or service entry. Ask the utility about any supply disturbance. Collect samples through a certified lab and follow the health authority's direction on use. Only after those steps should cartridges, softeners, and membranes be replaced or returned to service, and each reinstallation should be logged with its date, its part number, and the test result that cleared it. The order matters because each step produces a record that the next step depends on.
Further reading: coverage for home systems and appliances.