Water Heater Maintenance & Flush Schedule
The short, cheap maintenance routine that keeps a water heater at the top of its lifespan range – and how it shifts in hard water.
1 Enter your numbers
A yearly flush and a periodic anode check are the cheapest way to hit the top of the lifespan range. In soft water, descale a tankless more often. Follow the manufacturer’s maintenance instructions.
Water-heater maintenance is one of the highest-return, lowest-effort things you can do to a home appliance: an hour or two a year buys you the difference between the bottom and the top of the lifespan band. The routine is short and the same for most tanks – what shifts with your water is how often you descale.
The core cadence: flush the tank about once a year to clear sediment off the bottom; check the anode rod every 2–3 years and replace it once it is mostly eaten away; test the temperature-&-pressure (T&P) relief valve yearly; and on a tankless, descale the heat exchanger – every 1–2 years in soft water, but roughly yearly in hard water, where scale builds fastest.
Formula
There is no arithmetic here – this is a labeled cadence reference. The logic behind the intervals:
- Flush yearly – sediment accumulates continuously; a year is the practical balance between effort and buildup.
- Anode every 2–3 years – a magnesium/aluminum rod is consumed slowly; checking on this interval catches it before the tank itself starts sacrificing.
- T&P test yearly – a safety valve that never operates can seize; a gentle yearly test confirms it can still relieve.
- Descale by hardness – scale is a function of mineral load × throughput, so hard water compresses the interval.
Worked example
Take a household on hard water with a gas tank and a tankless in a rental next door. For the gas tank: flush this spring, and since it is due, pull and inspect the anode – if it is down to the steel core wire, replace it (about the cost in the anode replacement tool). Give the T&P valve its yearly test. For the tankless: because the water is hard, run a descale/vinegar-flush cycle yearly rather than every other year, or the heat exchanger loses efficiency and can throw scale-related fault codes.
Same two units on soft water: identical flush/anode/T&P routine, but the tankless descale can relax to every 1–2 years.
What to do, and what to skip
Two cautions that matter more than the schedule itself:
- The T&P valve is a safety device. Test it, but if it drips continuously afterward or will not reseat, replace it (see T&P valve replacement) – the discharge piping and code details are a plumber’s call, not a DIY guess.
- Gas and combustion are not on this list. Burner, flue, venting and combustion-air work are a licensed plumber / gas fitter and manufacturer-instruction matter, never a homeowner routine.
Common mistake: flushing a tank that has never been flushed and is a decade old. Disturbing years of hardened sediment can unseat a drain valve or reveal a corroded tank. If the unit is old and untouched, weigh a flush against simply planning the replacement.
Reference table
| Task | Cadence | Why |
|---|---|---|
| Flush the tank | About once a year | Clears sediment off the tank bottom |
| Check the anode rod | Every 2–3 years | Replace when mostly consumed |
| Test the T&P relief valve | Yearly | Confirms the safety valve still relieves |
| Descale a tankless | Every 1–2 years | Protects the heat exchanger & efficiency |
| Inspect fittings / pressure | Yearly | Watch for weeping and pressure spikes |
Labeled planning cadence – follow the manufacturer’s maintenance instructions for your specific unit.