How to Flush a Water Heater

Flushing drains the sediment that collects at the bottom of a tank water heater, which causes popping noises, less hot water and a shorter life. It takes about an hour with a garden hose, and supplies cost only about $10–$20.

Last reviewed September 2026

Step by step

1.Turn off the heater: switch off the breaker (electric) or set the gas valve to pilot or off (gas).
2.Let the water cool for a few hours, or wear gloves; tank water can scald.
3.Close the cold water supply valve on top of the heater.
4.Connect a garden hose to the drain valve at the bottom and run it to a floor drain or outside, lower than the valve.
5.Open a hot water tap somewhere in the house to let air in, then open the drain valve.
6.Let the tank drain. Briefly open and close the cold supply a few times to stir up sediment.
7.When the water runs clear, close the drain valve, remove the hose and open the cold supply to refill the tank.
8.Keep the hot tap open until water flows steadily without sputtering, then close it.
9.Restore power or relight the gas only once the tank is full, so electric elements don't burn out.

Safety: never turn the power or gas back on while the tank is empty, and keep children and pets away from hot draining water.

Water heater flush cost

US national ranges
Job	Typical cost
DIY supplies	$10–$20
Professional flushing or descaling	$150–$300

Still not enough hot water after flushing? See no hot water troubleshooting.

Water heater flushing questions

How often should I flush my water heater?

About once a year for most tank heaters, and more often if you have hard water or hear popping noises from sediment.

What if the drain valve won't close after flushing?

Sediment can keep a plastic drain valve from sealing. Try opening and closing it a few times to rinse it, then cap it with a garden hose cap; replace the valve if it keeps dripping.

Can I flush a tankless water heater the same way?

No. Tankless units are descaled by circulating vinegar or a descaling solution through service valves with a small pump. See the tankless repair guide.