How Do I Flush My Water Heater?

By Vernon Trollinger, October 23, 2017, Home Improvement, Save Money

Welcome to the How Do I Do This? series from Bounce Energy. Each month, we’ll dive into what it what you need to know to shop for, install, or repair those things in your home to keep your life affordable and convenient. Plus, you’ll (hopefully) learn some useful tips for other projects along the way.

How Do I Flush My Hot Water Heater?

If your water heater is sounding like a popcorn popper, then it’s very likely that you have sediment problem. Sediment in water heaters is lime scale that settles out of the water and builds up at the bottom of your water heater. With natural gas heaters, it can cause uneven heating on the tank that eventually causes leaks. With electric heaters, scaling can burn out the lower heating element. Periodically flushing out the lime and other sediments in the water heater tank improves the heater’s efficiency and the heater’s lifespan.

Most newer water heaters have cold water supply valves mounted upstream from the water heater.

  • Step 1: Turn off the cold water supply to your water heater. In some older homes, you may need to turn off the water where the main water supply line enters your home. If you have a water softener between your main supply line and the water, there should also be a supply shut-off valve there.
  • Step 2: Turn off or turn down the water heater thermostat. Some water heaters have a “vacation” setting. The goal here is to avoid having the heater turn on once all the water is drained out, especially for natural gas heaters, because heating it without water can damage the water tank. Older natural gas water heaters that don’t have electric ignition are easy to re-light but be sure to review any lighting instructions and follow all the safety guidelines.

Water tank drain valves are usually made of plastic to prevent burns. Unfortunately, they can get brittle with age.

  • Step 3: Connect a garden hose to the tank’s drain valve near the bottom of the heater. Make sure the other end of the hose leads somewhere safe outside or to a drain because you’ll be letting a whole lot of hot water run through the hose. If you’re letting the water drain outside, make sure it’s far enough from your foundation so that water doesn’t flow into your home’s crawl space. Since this is hot water, remember to also keep it away from any shrubs or other plantings. You don’t want your flowerbeds to look like someone spilled soup all over the place. If you’re concerned about all the hot water, you can turn off the water heater at the end of the day to let it cool overnight.
  • Step 4: Open all the hot water faucets. This will let the water drain from the heater tank faster. It’s the same effect as putting your finger tip on a soda straw and then lifting the straw out of a drink. Vacuum keeps the liquid trapped inside until you lift your finger tip.
  • Step 5: Open the water heater’s drain valve and let the tank drain. Be sure to check on the water as it flows out of the hose to keep an eye on how much sediment is flowing out. Also, make sure the water is going where you want it and keep away any small children or curious pets that get too close. Yes, 50 gallons is a lot of hot water.TIP— If you open the drain valve and no water flows, it’s possible that sediment has clogged the valve. If this happens, you’ll need to open the temperature pressure release to let off pressure from the tank and drain any water that’s left in the hot water pipes downstream from the heater. Next, use a wet/dry vacuum to suck some of the blockage out of the drain valve —at least enough to get the water flowing. Be careful to avoid getting splashed with hot water and wear gloves. If the blockage is bad enough that it won’t budge, you’re in for an arduous afternoon. You’re going to need to remove the temperature pressure release valve and suck out the water with the wet/dry vac and then replace the drain valve.
  • Step 6: After the tank is drained, turn the cold water supply back on. Because there will likely be some sediment in the bottom of the tank, running the cold water will help rinse it out. Let it run for just a few minutes and check the end of the hose to see when it runs clear. Then turn it off.
  • Step 7: Disconnect the hose from the tank drain valve and check for any sediment around the opening. Use a wet/dry vacuum to suck out any sediment from the drain valve. This will prevent it from fouling the valve when you shut it off. A little won’t do much harm to the valve but you want to clear enough out so that the valve doesn’t leak. Once you’ve closed the drain valve, turn the cold water supply back on.
  • Step 8: Leave the hot water faucets open until water begins flowing out of them. This will prevent air from becoming trapped. Don’t be surprised if you see rust or sediment coming out at first. Once the water clears (usually after a minute or so), it will be ok to turn the faucets off.
  • Step 9: Reset the water heater thermostat to your preferred setting. Once the tank is filled, you should have plenty of hot water in 15 to 20 minutes. Of course, that all depends on the size of your water heater, it’s overall efficiency, and whether it’s natural gas or electric.
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A native of Wyomissing Hills, PA, Vernon Trollinger studied writing and film at the University of Iowa, later earning his MA in writing there as well. Following a decade of digging in CRM archaeology, he now writes about green energy technology, home energy efficiency, DIY projects, the natural gas industry, and the electrical grid.

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