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Dishwasher: Food Grit Remains on Dishes

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  • Dishwasher: Food Grit Remains on Dishes

    The Problem
    Our GE Profile (PDW8480J10) dishwasher leaves food grit of a sand-like consistency on the dishes. I've attempted various solutions to this persistent, disgusting problem, which run the gamut from the simple (different detergents) to the complex (replaced the drain pump), but to no avail. The gritty stuff continues to speckle the insides of glasses and the surface of plates. I routinely dismantle the dishwasher innards to get at and clean the sump. After a few washes, the grit is back. Grrrr...

    I believe the drain pump is the most likely source of the grit in the dishwasher, and the thing that creates the grit in the first place.

    How dishwashers drain waste-water
    A 48" drain hose directly connects between the drain pump and the garbage disposal. The disposal outlet resides 14in higher than the drain pump, which means a significant amount of waste-water remains in the drain hose after the dishwasher has finished. (The drain pump has a rubber backflow valve to prevent waste-water backflow into the sump through the drain pump when it is not active.) The drain pump must generate sufficient pressure to raise a column of standing waste-water from the bottom of the dishwasher thru the length of the drain hose and then over a foot "uphill" to discharge into the disposal. All dishwashers pretty much work this same way.

    My theory
    I inspected the drain pump (WD26X10039) when I had it out. I noticed that the impeller has four flat paddles rather than curved vanes (think "turbine"). Seems to me, an impeller built with curved vanes would draw waste-water efficiently and thus propell the gunky stuff out of the dishwasher like it's supposed to. I have a theory that this specific drain pump mostly just churns the waste-water which renders food scraps into sand-like particulate, the heaviest of which never get pumped out of the machine do to the inefficient design of the pump. Indeed, the OEM replacement pump shares the same impeller design. Not surprisingly, replacing the pump did not resolve the problem.

    Anyway, anyone else had similar problems with their dishwasher? If so, did you discover a permanent solution?

    GE Profile (PDW8480J10) dishwasher
    Click image for larger version

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    drain pump (WD26X10039)
    Click image for larger version

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    Last edited by lothian; 09-07-2012, 08:35 PM. Reason: corrected a few grammar errors

  • #2
    I have a theory that this specific drain pump mostly just churns the waste-water which renders food scraps into sand-like particulate, the heaviest of which never get pumped out of the machine
    That wouldn't explain how it got back into the machine.


    How hot is the water in the machine? Do you run a sink tap until hot before starting the dishwasher?

    The dishwasher should have 120-140 deg. F water for best washing. If it starts filling with cold or luke warm water before it gets up to hot, the water temperature inside the dishwasher will be considerably colder than needed for proper washing.


    How high is the water in the machine right after a fill? It should usually fill to just below the heating element.


    Is the dishwasher filling for any rinse cycles after the initial fill?


    Have you made certain the drain hose is not blocked in any way?


    Dan O.
    Appliance411.com
    The Appliance Information Site

    =D~~~~~~

    .

    Comment


    • #3
      "That wouldn't explain how [the grit] got back into the machine."
      I speculate that since food grit originates in the sump it may get drawn out and recirculated by the wash motor, which is stronger than the drain pump.

      "How hot is the water in the machine?"

      The dishwasher automatically raises the wash water temp, a feature called "CleanSensor". Using a digital oven thermometer, I read the wash water temp at ~140° on the "Normal" cycle, and ~175° on the "Anti-bacteria" cycle.

      "How high is the water in the machine right after a fill?"
      Water fills to just below the heating element.

      "Is the dishwasher filling for any rinse cycles after the initial fill?"
      Yes. It fills (and drains) during every rinse cycle.

      "Have you made certain the drain hose is not blocked in any way?"
      The drain hose is not blocked, nor is the drain pump clogged.


      I may troubleshoot the turbidity sensor (WD21X10202) next.
      Last edited by lothian; 09-11-2012, 01:07 PM. Reason: corrected a couple grammar errors

      Comment


      • #4
        I don't know about on your exact model but the turbity sensor could extend the length of a wash cycle. Its operation and test proceedures may be described in the dishwasher's tech sheet which should accompany the unit's wiring diagram.


        Dan O.
        Appliance411.com
        The Appliance Information Site

        =D~~~~~~

        .

        Comment

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