Cold water “bang” in water heater

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    • #276979
      Avatar photoGarrett Lane


        Ranch house, 1 bath. New plumbing and fixtures throughout. When any cold (not hot) water faucet
        is turned off (manually or automatically ie. washer) a
        loud knock (bang) is heard on the cold water side of the
        water heater, followed by several metallic noises of
        diminishing intensity. Like if you’d push a pipe hanging on a string into a wall and listen to it hit over and over until it stops.

        Think it might be the drip tube hitting something, but
        not sure. Installed water hammer arrestor on toilet
        (before the shut off valve) as an experiment, but it didn’t help.

        Any thoughts? Water heater is level. New 40 gallon Hotpoint Powervent.

      • #295173
        Avatar photoDUNBAR

          You need to shut heater to pilot…..use the pressure of the main and first open boiler drain at bottom of heater to clear the drain.

          Once drain is running free, shut cold water valve off at top of heater and open any hot water valve above heater or around it.

          That is sediment cooking at the bottom of tank and shutting off of water abruptly shakes this up.

          When hose is connected to heater…….use your foot and pulse water out of heater with water valve open to jolt the sediment off the bottom of tank.

          You can’t get all of it……….but usually a good deal.

          If the heater has more than five years of age….I would not suggest this; it would be like taking leaves out of a garbage can with the bottom rotting out…… is going to rust out that much quicker now that the metal is uncovered.

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