How to Flush Your Water Heater
in 8 Simple Steps

By: Kealia Reynolds
Residential Water Heater with the panel removed for repairs or adjustments to the thermostat. Please also see my lightbox:

You use your water heater more frequently than any other appliance in your house. By learning how to flush your water heater, you’ll prolong its lifespan and save money.

The US Department of Energy recommends flushing one quart of water from tank-based heaters every three months. Here’s your step-by-step guide to test—and drain—your water heater to keep it in best working order. Plan 25–75 minutes for this project.

Materials

  • Garden hose
  • Large pan or bucket
  • Towel
  • Flat head screwdriver
  • Protective gloves

Safety considerations and lifetime of water heaters

You will be dealing with extremely hot water throughout this process. Make sure you wear heavy-duty gloves and long-sleeved clothing to prevent scalding water burns. Read the manufacturer’s manual before beginning maintenance or repairs. This could help prevent a possible fire, explosion, or personal injury.

If you feel uncomfortable flushing your water heater on your own, call in a pro. Professionals tend to charge $170–$230 to flush a water heater.

Water heaters last an average of 8–15 years, so if you’re experiencing issues with the process, it may be time for an update. Constant water temperature issues or pressure, a milky texture in the tank, or brown sediment emerging from the faucet when the hot water is turned on, are all signs that it’s time for a replacement.

How to flush a water heater

1. Turn off your system

2. Close cold water supply valve

This valve is located at the top of your water heater and is often marked with blue tape. Turning off this valve, will prevent any additional water from entering your tank while it is draining.

3. Relieve system pressure

Open a hot water faucet elsewhere in your home. This relieves system pressure inside the tank and prevents a vacuum from forming in the water lines. Leave the faucet on for the duration of  the flushing process.

 

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4. Open pressure relief valve

Though this step isn’t necessary, we do recommend it. Opening the pressure relief valve can help water in the tank drain more quickly. If you choose to complete this step, place the bucket underneath the valve to catch any water that comes out. As this water will be coming from the storage tank, it will be extremely hot. Exercise caution when opening the valve. Use the towel to wipe up any excess water spilled from opening the valve immediately.

5. Connect garden hose to drain valve

Screw in the garden house to the drain valve and run the end of the hose outside or into a drainage bucket. Make sure the receptacle can accommodate the full capacity of your storage tank—when possible, drain directly into a sewer system.

6. Open drain valve

Most water heaters will come with a knob to open the drain valve—if yours doesn’t have this knob, you’ll need to grab the flat head screwdriver to open the valve. Once open, drain 2–3 gallons of water. If the water is milkly, drain the entire storage tank. Flush the full storage tank every 1–3 years.

7. Flush

Keep the garden hose attached to the drain valve. Open the cold water supply valve. Let the water supply run for 3–5 minutes, checking the water draining from your system. Once clear, close the drain valve and disconnect the garden hose. Close the pressure relief valve if you opened it in step four.

8. Finish

Wait for the storage tank to fill completely. Open the pressure relief valve again to release air that accumulated in your system, then close it. Check the faucet that was turned on during step three—cold water should be running. Then, turn it off. If you shut off the gas to your gas water heater, turn it back on. Relight the pilot light if needed on older model heaters. If you shut off electric, turn the corresponding breaker back on to restart your water heater. Wait for 20–30 minutes. Turn on a hot water faucet to ensure the water is hot.

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