The Ultimate Guide to Water Heater Maintenance and Understanding

Our water is hard, which means dissolved minerals settle out inside the tank as it heats. That sediment forms an insulating layer on the bottom, so the burner or lower element has to work longer to heat the same water. You feel it as slower recovery and see it on the power bill before you ever see a leak.

Sediment also traps heat against the steel, which stresses the glass lining and the sacrificial anode rod that protects the tank from corrosion. Once that anode is spent, the tank itself starts corroding — and a corroded tank cannot be repaired.

Two jobs matter more than everything else combined: flushing the tank and checking the anode rod.

Rusty or metallic-tasting hot water, popping and knocking during heating cycles, hot water that runs out sooner than it used to, or any moisture at the base of the tank. A rumbling tank is sediment; rust in the water is usually the tank itself.

Water pooling under the unit is not a wait-and-see problem. Tanks fail from the bottom, and a slow seep is often days from becoming a full release of 40 to 80 gallons onto your floor.

Thermostats, elements, gas valves, and relief valves are all repairable, and on a heater under about eight years old repair is usually the right call. Once the tank is leaking, or the unit is past ten years with hard-water history, replacement is the honest answer — you'd be spending repair money on a tank that's already thinning.

If you're replacing anyway, it's the right moment to ask about sizing and about tankless. Tankless units cost more up front, take up less space, and don't store water that can fail — but they need adequate gas supply or electrical capacity, and in hard water they need periodic descaling to hold their efficiency.