Water heater maintenance, ranked by what it actually saves

Flush the sediment out — the routine task

Minerals settle out of heated water and collect on the tank floor. On a gas unit that layer sits between the burner and the water and makes the burner work through it; on an electric unit it buries the lower element. A flush drains the tank through its drain valve, ideally with the supply briefly reopened to stir the bottom before the final drain. How often depends on your water, not on a universal schedule.

Watch for: A drain valve that will not reseat afterwards. The cheap plastic valves fitted to many tanks are a one-way trip once sediment gets into the seat, so have a replacement valve on hand — or a professional doing it — on any tank that has gone many years untouched.

Inspect the anode rod — the task that decides tank life

The anode is a sacrificial rod that corrodes preferentially so the steel tank does not. Once it is consumed, the tank lining is on its own and the clock speeds up considerably. Replacing a spent rod is inexpensive relative to a new heater and is the most cost-effective thing you can do to a storage tank. Nobody advertises it because it is a small job that prevents a large sale.

Watch for: A rod that has been in place for many years and is now seized into the tank. It often needs substantial torque and real clearance above the unit to withdraw. Tight basements sometimes need a segmented rod, and that decision should be made before the wrench comes out.

Test the temperature and pressure relief valve

The T&P valve is the appliance's last-resort safety device, and it can seize shut over years of never operating. The test is brief — lift the lever, confirm water discharges freely, confirm it stops when released. It should also be verified that the discharge line runs full-size, downward, and terminates where it is allowed to.

Watch for: A valve that will not reseat and now drips permanently after testing. This is a real risk on old units, which is why it is worth doing when someone is there who can replace it on the spot rather than on a Sunday afternoon alone.

Descale a tankless unit

Tankless units accumulate scale on the heat exchanger rather than sediment in a tank. Descaling circulates a solution through the exchanger via the isolation valves, and frequency follows water hardness rather than the calendar.

Watch for: No isolation valves fitted at install. Without them the service becomes a plumbing job every time, which is exactly why so many tankless units never get descaled at all until they start failing.

Check the parts nobody looks at

While someone is there: the pan and its drain, the expansion tank, corrosion at the connections, and on a heat pump unit the air filter and condensate route.

Watch for: An expansion tank nobody has assessed. They fail internally with no external sign, and the first symptom is a dripping relief valve that gets blamed on the valve.