Water heater maintenance: what to do and how often
A tank water heater typically lasts eight to twelve years. Maintained, it reaches the top of that range and sometimes beyond. Ignored in a hard-water area, it can fail in six — often by leaking, at the least convenient moment, onto a floor you cared about.
The whole maintenance programme is about an hour a year.
Safety first
Before anything else: water heaters combine scalding water, and either gas combustion or high-current electricity. Turn off the power at the breaker (electric) or set the gas control to pilot or vacation (gas) before draining. Let the water cool. If you are not confident, this is an inexpensive job for a plumber — and much cheaper than the alternative.
Annually: flush the tank
This is the single most valuable thing you can do.
Minerals in the water settle out and form sediment on the tank floor. In a gas heater, that sediment sits between the burner and the water, so the burner runs longer and hotter to heat through it — wasting energy and stressing the tank. In an electric heater, sediment buries the lower element and burns it out. Sediment is also what causes the popping and rumbling noises people learn to ignore.
Roughly:
- Turn off the power or set gas to pilot.
- Shut the cold water supply valve.
- Attach a hose to the drain valve at the bottom and run it somewhere safe.
- Open a hot tap in the house to let air in.
- Open the drain valve and let it run until it comes clear.
- Briefly reopen the cold supply to stir up remaining sediment, and drain again.
- Close the drain, refill fully — the hot tap runs steadily — then restore power or gas. Never energise an electric heater that is not full.
In hard water, twice a year is better than once.
Annually: test the T&P relief valve
The temperature and pressure relief valve is the tank's safety device. If pressure climbs and the valve is seized, the consequences are severe.
Put a bucket under the discharge pipe, lift the lever briefly, and let it snap back. Water should rush out and stop cleanly. If nothing comes out, or it dribbles afterwards and will not seal, the valve needs replacing — that is a plumber job, and not one to defer.
Every 2–3 years: check the anode rod
The least known and most important part of the whole system.
The anode rod is a sacrificial metal rod inside the tank. Corrosion attacks it instead of the steel tank walls — that is its entire purpose. Once it is consumed, corrosion moves on to the tank itself, and a corroded tank cannot be repaired, only replaced.
Checking it every two to three years and replacing it when it is mostly eaten away — a part that typically costs tens of dollars — can add years to a tank that costs well over a thousand to replace. In hard water or with a softener, check more often; softened water is harder on anode rods.
Occasionally: check the temperature setting
Around 49 °C / 120 °F is the usual recommendation. Lower wastes less energy and reduces scalding risk, particularly with children in the house. Going much below that is not advised, because higher temperatures suppress bacterial growth in the tank. If anyone in the household is immunocompromised, take medical advice on the right setting.
Tankless heaters
Different job, same principle. Tankless units need descaling — circulating a descaling solution through the heat exchanger — every one to two years, more often in hard water. They also have an inlet screen filter that needs periodic cleaning. Skipping this is the main reason a tankless unit underperforms or fails early.
Warning signs to act on
- Any water around the base. A leaking tank is not repairable. Plan the replacement now rather than after the flood.
- Rusty or brown hot water — often a spent anode rod, or a corroding tank.
- Rumbling or popping — heavy sediment.
- Running out of hot water sooner than it used to — sediment volume, or a failed element.
- Rising energy bills with no change in use.
- Age past about ten years, with any of the above. Replacing on your schedule costs far less than replacing on the tank's schedule, because an emergency replacement means emergency rates plus whatever the water damaged.
Put it on a schedule
None of these jobs announce themselves. A water heater gives no warning that the anode rod is gone; it simply fails a few years earlier than it should have. Annual flush, annual valve test, anode rod every two to three years — set once as repeating tasks, and the machine quietly lasts longer.
Worth recording the install date and the warranty length too. Tank warranties commonly run six to twelve years, and a tank that fails inside that window is often replaced free — but only if you can prove when it went in. See what counts as proof of purchase.
Keepit remembers this so you don't have to
Put the annual flush and the anode rod check on a repeating schedule — they are exactly the jobs that get forgotten until the basement is wet.
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