How to Flush a Water Heater (Step-by-Step Guide 2026)

Flushing your water heater is the single most important maintenance task you can perform to extend its life. Over time, calcium and other minerals in your water supply settle at the bottom of the tank, creating a layer of sediment. This sediment acts as an insulator, making your heater work harder and increasing your energy bills.

In this guide, we’ll walk you through the professional-approved method for flushing both gas and electric water heaters.

Tools You’ll Need

A garden hose (or a specialized flushing hose)
A flat-head screwdriver
A bucket (optional, for checking sediment)
A utility pump (only if your heater is in a basement with no floor drain)

Step 1: Turn Off the Heat Source

Before you touch any water valves, you must disable the heating system.

For Electric Heaters: Turn off the circuit breaker in your home’s main electrical panel.
For Gas Heaters: Turn the thermostat knob to the “Pilot” or “Off” setting.

Step 2: Shut Off the Cold Water Supply

Locate the cold water inlet pipe (usually marked with a blue ring or handle) and turn the valve to the “Off” position.

Step 3: Connect Your Drainage Hose

Attach your garden hose to the drain valve at the bottom of the tank. Run the other end of the hose to a floor drain, a sump pit, or outside.

Step 4: Open a Hot Water Faucet

Go to a nearby sink and turn on the hot water. This allows air into the system, preventing a vacuum and letting the tank drain faster.

Step 5: Open the Drain Valve

Carefully open the drain valve using your screwdriver (or by hand if it has a handle). Warning: The water will be extremely hot!

Step 6: The “Flash” Flush

Once the tank is empty, turn the cold water supply back on for 30 seconds while the drain valve is still open. This “flashes” the bottom of the tank, stirring up and washing out any remaining stubborn sediment. Repeat this until the water from the hose runs clear.

Step 7: Refill and Restart

Close the drain valve.
Disconnect the hose.
Turn the cold water supply back on fully.
Wait until water flows steadily from the open hot water faucet (this ensures the tank is full and air is out).
Turn the power or gas back on.

Why Flusing is Essential

Sediment buildup can lead to “tank knocking” (the sound of steam bubbles exploding through sediment) and can eventually rot the bottom of your tank, leading to catastrophic leaks. By flushing once a year, you can easily double the lifespan of your unit.