Hot Water Heater Flush......advice

Discussion in 'Water Heater Forum, Tanks' started by chefwong, Sep 20, 2010.

  1. chefwong

    chefwong Member

    Jun 14, 2006
    District of Columbia
    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. Gary Swart

    Gary Swart In the Trades

    Sep 1, 2004
    Yakima WA
    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.
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  4. SteveW

    SteveW DIY Senior Member

    Feb 11, 2005
    Omaha, NE
    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.
  5. Runs with bison

    Runs with bison Member

    Aug 23, 2009
    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.
  6. ballvalve

    ballvalve General Engineering Contractor

    Dec 28, 2009
    "retired" and still building and troubleshooting
    northfork, california
    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.
  7. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    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).
  8. jham123

    jham123 New Member

    Oct 12, 2010
    Irvine Ca
    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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