How to Flush a Water Heater (and Why You Should)

Minerals in water settle to the bottom of a tank water heater as sediment. Over time it insulates the water from the burner or elements, so the heater works harder, makes popping or rumbling noises and wears out sooner. Much of Florida has hard water, so this matters here.

How often to flush

Once a year for most homes. Every six months if your water is very hard or you see white flakes in faucet aerators.

Before you start: safety

• The water is hot enough to burn. Let it cool for a few hours, or run hot water first.
• Read the label and manual for your model.
• Electric heater: turn off the breaker. Never run the elements with the tank empty.
• Gas heater: turn the gas control to pilot or off as the manual says.

Step by step

1. Turn off the power or gas as above.
2. Turn off the cold water supply at the top of the heater.
3. Connect a garden hose to the drain valve near the bottom and run it to a floor drain or outside to a spot where hot water will not hurt plants.
4. Open a hot water faucet in the house so air can enter the tank.
5. Open the drain valve and let the tank empty.
6. Flush: turn the cold supply on briefly with the drain open to stir up sediment, and repeat until the water runs clear.
7. Close the drain valve, remove the hose and turn the cold supply back on.
8. Wait for the tank to fill. When water flows steadily from the open hot faucet, close it.
9. Restore power or gas only after the tank is full.

While you are there

• Test the temperature and pressure relief valve per the manual.
• Look for rust, leaks or water under the tank.
• Ask a plumber to check the anode rod every few years. It protects the tank from rust, and replacing it can add years of life.

Signs it is time for a new water heater

• Tank older than about 10 years
• Rusty hot water
• Water leaking from the tank itself
• Not enough hot water even after flushing

Frequently asked questions

Do tankless water heaters need flushing?

Yes, a descaling flush with a pump and solution, usually once a year with hard water. A plumber can do it.

What if the drain valve will not close?

Old plastic valves can stick or leak. Cap it with a hose cap and call a plumber to replace it.

Post your water heater job for a flush, repair or replacement, and get bids from local plumbers.