How Often Should You Flush a Water Heater?
4 min read · Updated 2026-07-07
Short answer: once a year for a standard tank water heater — more often (every six months) if you have hard water. It is one of the highest-value maintenance tasks in the house: a 30-minute job that protects a $1,200–$2,500 appliance.
Why sediment is the enemy
Minerals in your water — mostly calcium and magnesium — settle at the bottom of the tank over time. That sediment layer forces the burner or heating element to work through an insulating blanket of scale, which raises energy use, causes rumbling or popping noises, and shortens the life of the tank.
Left long enough, sediment can clog the drain valve, corrode the tank bottom, and turn a routine flush into a replacement.
How to flush it (30 minutes)
Turn the thermostat to "vacation" or pilot (gas) or switch off the breaker (electric). Turn off the cold-water supply. Connect a garden hose to the drain valve at the base and run it to a floor drain or outside. Open a hot tap somewhere in the house to break the vacuum, then open the drain valve and let the tank empty. Briefly reopen the cold supply to stir up remaining sediment and drain again until the water runs clear. Close the valve, refill the tank, then restore power or the thermostat setting.
If the tank has never been flushed and is more than five years old, open the drain valve gently — heavy sediment can clog an old valve. If nothing drains, call a plumber rather than forcing it.
Signs you have waited too long
Rumbling, popping, or crackling as it heats; hot water running out faster than it used to; rusty or sandy water from hot taps; a rising energy bill with no other explanation. Any of these means flush it soon — and if the tank is 10+ years old with these symptoms, start budgeting for a replacement.
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Frequently asked questions
How often should I flush my water heater?
Once a year for most homes. With hard water, every six months. Tankless units also need annual descaling with a pump kit.
How long does a water heater last?
Tank units typically last 8–12 years; tankless units 15–20 with regular descaling. Regular flushing pushes you toward the high end of the range.
Can flushing an old water heater cause leaks?
Rarely — but on a neglected 10+ year tank, sediment can be what is plugging a weak point. Drain gently, and if the drain valve will not close afterward, cap it and plan service.
Is flushing worth it on a brand-new water heater?
Yes. Starting annual flushes in year one keeps sediment from ever building a hard scale layer — that is what doubles usable life.