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I have heard many times that it is good to clean your hot water heater about once a year by flushing it. I went to look online to find the proper way to do so and found many people recommending different things for how to clean it.

  • Turn off the water supply and drain the heater completely
  • Turn off the water supply and drain the heater by just a couple gallons, then turn the water on and off a few times to try to stir up anything at the bottom to let it drain
  • Leave the water supply on and run water out of the heater until it clears up

Most of the posts I found recommended the last option, so I decided to go this path. What I found was that all of the water coming out of the hose wasn't very warm (as in it was coming almost directly from the cold water supply) and it seemed to be very clear.

Did I do it right? What is the proper way? As a note, I have a gas water heater that is about 4 years old.

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on your next maintenance have the guy flush it for you and ask how to do it yourself –  ratchet freak Jan 22 '12 at 23:41
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with a gas heater it's prudent to have it serviced regularly (you don't want it leaking gas when it can be avoided) –  ratchet freak Jan 23 '12 at 0:07
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I've never had any of my gas water heaters serviced. If you have a gas leak, you should smell it, or recognize the tell tail kaboom. –  BMitch Jan 26 '12 at 0:17
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@BMitch it's not only a leak that you should be worried about. CO poisoning is a real threat with any fuel based heaters and your insurance will be the first to point out that the installation hadn't seen a licensed maintainable guy when you see the kaboom –  ratchet freak Feb 9 '12 at 18:04
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@ratchetfreak, I'll be the first one to suggest you get a CO (carbon monoxide) detector wherever you have gas utilities any near any fireplace. Not saying that servicing a WH is bad, but it's probably overkill. –  BMitch Feb 9 '12 at 18:58
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2 Answers

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+50

Not sure there's a right way, just people with different preferences. Here's what I think is important:

  • You need water entering the tank from the cold side, so it should be open for most of the process. The cold line goes to the bottom of the tank, which is where the sediment will be. I personally turn my supply off when first opening my drain in case that valve malfunctions, but I've got a pretty cheap drain valve.
  • You want as much pressure going through the cold input to kick up the sediment, so try to leave all the valves open as much as possible. If your drain is a little slow, then opening and closing the cold shutoff might be a good way to get more sediment stirred up.
  • Monitor the discharge. On my next cleaning, I plan to run the hose into the utility sink next to the hot water heater so I can watch the result. Without doing this, you're missing a key piece of data to know when you can stop. I'd run 5 or so gallons after you see it start to run clear.
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And for long life, pull the anode rod every so often and check to see if you can see the iron center that runs down through the Zinc or Aluminum sacrificial metal. A good portion of the sediment you are flushing is material off this rod which is there to prevent the tank from rusting through. The manual that came with the water heater will tell you how to do this. Usually there's an access hole in the top cover with an insulation plug. The Anode looks like a metal plug, but when you unscrew it, you should find a rod about 2-3 feet long in various stages of erosion. Iron Wire bad, tank rusted. –  Fiasco Labs Aug 26 '12 at 16:22
    
I would suggest not running the water into the utility sink. The sediment/scale could clog your drain. –  Les Dec 4 '13 at 19:13
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Here's how I cleaned my heater. Close inlet valve. Drain all the water (I opened pressure relief valve to vent). Replace drain valve with a gate valve and garden hose fitting. Use a plumbers snake to "stir up" sediment. Connect drain hose. Close pressure relief valve. Open water inlet. When water runs clear, turn off inlet value. Allow tank to drain. Start over with snaking tank. Repeat until good enough for you.

If your situation allows, you can run the snake with the inlet water on, greatly reducing the time for cleanout. This gets rather messy.

As added security, I installed a garden hose end cap onto the garden hose connection when I was done.

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