San Diego's hard water drops sediment into every tank and scale onto every tankless heat exchanger — the main reason local water heaters die years early. An annual flush (tank) or descale (tankless) plus an anode rod check is the cheapest insurance in plumbing. Companies offering maintenance plans are flagged in the directory.
Every gallon heated in San Diego drops a little calcium and magnesium. In a tank it settles as sediment, hardens into scale, and forces the burner to heat through a crust — stealing capacity and years. In a tankless unit it coats the heat exchanger and chokes flow. A maintenance schedule a soft-water city could skip is simply not optional here.
A drained flush of the sediment, a look at the anode rod — the sacrificial part that corrodes so the tank does not — a test of the temperature-and-pressure relief valve, and a check of the burner or elements and temperature setting. For tankless, the equivalent is a circulated descaling solution. Fifteen-minute "flushes" that skip the anode and the T&P valve are theater.
Tanks here that never see a flush land at the short end of the 8-to-12-year range; maintained units reach the long end, and a fresh anode rod can push past it. On a tankless unit, annual descaling protects both performance and the manufacturer warranty. Against the price of an early replacement, an annual service visit is rounding error.
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Once a year for most homes — the hard water here drops sediment faster than soft-water regions, so the national "every few years" advice undershoots. A tank that has never been flushed should be serviced soon, though long-hardened sediment sometimes cannot be fully removed.
It is a sacrificial metal rod inside the tank that corrodes in place of the steel. Once it is depleted, the tank itself starts rusting — and that is irreversible. On San Diego water, having it inspected during the annual flush, and replaced every three to five years, is what gets a tank to the long end of its lifespan.
Yes, arguably more. There is no tank to flush, but hard water scales the heat exchanger, chokes flow, and triggers error codes. An annual circulated descale restores performance, and several manufacturers expect documented descaling to honor warranty claims on hard water. Skipping it is the most common tankless mistake locally.