Water heaters
How to Flush a Water Heater (and When to Call)
Updated · Kestrel editorial
Short answerTurn off gas or power, close the cold inlet, attach a hose to the drain valve, open a hot faucet, drain until water runs clear, then refill before restoring heat. Call a plumber if the drain valve leaks, won't open, or the tank is very old.
Steps
- Turn off gas (pilot setting) or the breaker
- Close the cold water inlet
- Hose from drain valve to a floor drain
- Open a hot faucet and the drain valve
- Flush until clear, then close and refill
- Restore gas or power
When to stop
Old plastic drain valves can break. If it leaks or the water is rusty, call for water heater repair.
When not to flush
If the drain valve is plastic and very old, or the heater hasn't been flushed in many years, opening the valve can cause a leak it won't reseal. In that case, have a plumber flush it and replace the valve.
How to Flush a Water Heater (and When to Call): follow-up questions
How often should I flush a water heater?
About once a year for most homes; more often with very hard water.
Why does my water heater make popping noises?
Sediment on the bottom of a gas tank traps water that boils and pops. Flushing usually helps.
Every home differs; editorial standards.