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Thread: Hot Water Heater Flush......advice

  1. #1
    DIY Senior Member chefwong's Avatar
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    Default Hot Water Heater Flush......advice

    Just trying to do a flush on my hot water heater....ahem....Sears Powermiser 12 - Gas

    With the cold water off, only a pint of water comes out...
    I was under the impression to flush the tank, the cold feed needed to be off.

    Am I missing a step here.

  2. #2
    In the Trades Gary Swart's Avatar
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    How will it flush if there is nothing pushing the water out? Not only do you need the incoming water to flush the tank, when you turn the intake valve off, you create an air lock. It's kind of like a giant soda straw that is full of water. It won't drain as long as you hold you finger over the top. It is likely there is sediment at the bottom of the tank and you will need to run a stiff wire through the drain valve to help break it loose, but the intake must be on not only to supply the flush water, but to keep from having an air lock. If there is shut off valve on the hot water side, turn if off otherwise just keep the hot water faucets off in the house.

  3. #3
    DIY Senior Member SteveW's Avatar
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    You can also open the TPR valve to allow air to enter the tank. After the tank is drained, you can close the TPR valve and open and close the cold water inlet valve to flush out the residue in the bottom of the tank.

    Like Gary says, you may (in fact, likely will) get sediment clogging your drain valve especially if you haven't flushed the tank for a while. If so, you may end up replacing the drain valve. If you need to do so, I'd recommend getting a full-port 1/4 turn valve to prevent the problem in the future.

    Make sure you turn off the gas before draining the tank.

  4. #4
    DIY Senior Member Runs with bison's Avatar
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    Be careful if that is a plastic drain valve...they can become very brittle. Roughly a decade ago I had one that developed what appeared to be a packing leak, when I tried to *gently* tighten the packing it immediately sheared--I literally had barely touched the thing.

    We had some discussion about a year ago about replacing these with a brass quarter turn valve. Ideally one would want a full open bore, straight run to a drain at full line pressure for the blowdown of scale or sediment, but that's often not practical.

  5. #5
    General Engineering Contractor ballvalve's Avatar
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    All the drain down valves on Water heaters are pure trash. Plastic that break with 1/8" ports, or metal that freezes with 3/16 ports.

    Either replace them with a ballvalve, or remove the lower element and attach a short piece of garden hose to your shop vac and start shoving, rattling and sucking. Got 5 gallons of calcium crust one time. look inside with a maglite - amazing collection of junk that the MFG does NOT want you to get out.

    When I start making a water heater, you will get a 1.5" BRASS plug at the bottom for a clean out.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    The NEXT water heater I flush will probably be the first one. If the heater is flushed, it will probably last 10 years or so, if it is not flushed, it may only last 120 months, (mine will be 132 months in a couple of weeks).

  7. #7
    DIY Junior Member jham123's Avatar
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    Quote Originally Posted by SteveW View Post
    I'd recommend getting a full-port 1/4 turn valve to prevent the problem in the future..
    This is the ticket. That sediment comes out in clumps. Look at the tiny hole in that plastic valve that comes stock....nothing can fit.....the larger hole on the 1/4 turn valve is the way to go.

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