How To Clean and Flush a Water Heater

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The way a water heater works, cold water enters through a dip tube that runs down to the bottom of the tank and hot water exits from the top of the tank. This results in sediment, rust, and contaminants from the water sinking to the bottom of the tank where it builds up over time.

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Allowing the sediments and calcium deposits to build up in the tank may result in loss of heating power, failed components such as clogged pipes or the heating element, and possible health issues for those who use the water. To get the safest and most dependable use from your water heater, cleaning it annually is the best way to go. Here’s how to flush a water heater…

Related: How to Flush a TANKLESS Water Heater

Drain the Water Heater

Connect a garden hose to the hose bib near the bottom of the water heater and extend the hose to a floor drain or outside location.

Note: If you have a drain pan underneath that is correctly plumbed to a drain, no hose is necessary.

dirty-water-heater-sediment

Turn off the power to the water heater or set the gas control valve to the “Vacation” setting. Close the cold water inlet valve which is usually located at the top of the tank. Open the drain valve and turn on the closest hot water faucet to allow air into the tank.

See Also:  6 Ways to Unclog a Water Heater That Won’t Drain

Allow the tank to empty fully before proceeding. Obviously, larger hot water heater sizes will take a bit longer to drain but it shouldn’t take more than a few minutes.

Remove the garden hose from the drain valve. If your water heater has a plastic drain valve, this is a good time to replace it with a more durable brass valve. Using a large adjustable wrench, remove the drain valve and replace with the brass valve.

Cleaning and Flushing the Tank

Your local hardware store will sell a long, narrow brush (like this) that is designed for refrigerator coils but is also excellent for water heater tank cleaning.

Insert the brush into the opening where the drain valve was removed. Carefully use the brush to scrape the bottom of the tank and as much of the interior sides of the tank as you can reach.

If your tank has not been cleaned in a while, this can take a bit of time. The more of the sediments you can break loose, the better your water heater will function.

Screw a short 3/4 inch plumbing nipple into the drain opening. Drain valves are not suitable for tank cleaning because they are easily clogged by the debris that will be flushed out.

Place a bucket directly below the plumbing nipple or connect a garden hose to the other end of the nipple (or let it drain into a properly installed drain pan). Insert the other end of the hose (if using one) into a bucket so you will be able to see the results of your cleaning.

Turn on the cold water inlet valve and allow it to run until the water coming out of the hose clear. Remove the nipple and repeat the process until no more sediments are washed out after scrubbing. There may be rust, calcium deposits or other debris in the bucket.

Note:  Many newer water heaters include “self-cleaning” feature. While helpful, you still want to manually flush and clean a water heater but you simply don’t have to do so as often. So instead of an annual cleaning, doing so every 3 years or so should suffice.

Completing the Project

Turn off the hot water faucet. Instead of replacing the drain valve, you can install an inline ball valve on the end of the nipple to make future cleaning easier. You will need to add a second, short nipple to the outlet side of the valve.

Wrap the threads on both ends of the nipple with plumber’s tape and tighten the nipple securely into the tank. Screw on the ball valve and tighten it properly.

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Turn on the cold water inlet valve. Turn on the hot water faucet and allow it to flow until all air has escaped the line. When the air has been removed from the tank, restore power or set the gas control valve to the “On” position.

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Comments

  1. I wouldn’t stick anything up there — draining your water heater once a year is quite sufficient. Water should not come out that nasty looking if you do it yearly even with hard water. Mine comes out somewhat cloudy only then clear.

    Reply
    • True… IF you’re diligent about an annual cleaning. I would bet most homeowners have never drained a water heater tank but it’s a great (and easy) preventive measure.

      Reply
    • Dont forget about those of us that bought a house with no way of knowing if the hw tank was ever maintained! Mine had little debris, but more than its share of slime.

      Im never opening my mouth in the shower again.

      Reply
  2. I had no idea you were supposed to clean out a water heater every year. I came here because my water heater had a slow leak for some time. Our water heater is as old as our house (almost 10 years). Do you think the inside of tank is now all messed up because we’ve never cleaned/flushed it?

    Reply
    • I think you have already *REPLACED* your water heater… Leaks seldom if ever ‘fix’ themselves, and are fairly awkward and messy to consciously *fix*, so are usually rectified by replacing the unit…

      Reply
  3. The fastest and easiest way to clean a water heater is with a Turbo Tank Cleaner tool. Check it out at turbotankcleaner.com.
    It’s the only way to go!!!

    Reply
    • So, I tried to follow this procedure. Tank looks likes it’s 2009 vintage, but in very good shape externally. Moved in last year and have to assume it’s never been done before. Drain valve is a nice brass one. When doing the drain I never got a really good flow out of the hose, 2 hot water taps open. Only had a trickle of hot water…certainly not 40 gallons. Does that mean it’s too late….bottom already fully caked up on the bottom?

      Reply
      • There are a few things you can try. Using the brush that’s mentioned in the article is a good one. Another idea, with a hose connected to the drain valve, you can try stepping hard (or jumping) on the hose multiple times a few feet away from the tank. This will push air/water back into the tank to possibly help unclog it. If you have an electric water heater, you can possibly remove the lower heating element and drain through there (obviously make sure the power is off. Then you can use a wet/dry vac to do the rest. Here’s a good how-to: https://www.youtube.com/watch?v=VvSgfZF_cZ8

        Reply
  4. We can’t afford a new tank at this time and ours is full of sediment. Can a plumber buy us some time by cleaning the tank as much as possible?

    Reply
    • Yes, absolutely or you can even do it yourself. A cleaning brush, as shown in the article above, will allow you to get rid of more sediment than simply draining the tank.

      Reply
  5. My question is about sediment. I know fir sure there is plenty in this 4 year old tank. Once I use the hot water and the tank needs to reheat there is a loud boom and sounds like popcorn popping. The plumber drained it twice and said he found nothing coming out. But it still does this. He didn’t use any other tools, just the hose. And now I have air in pipes causing a lot of troubles with water flow and outdoor water spigot not having water flow, and it cause the water meter and attached pipes to shake. Help

    Reply

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