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How does pool chlorine/filter do its thing?

  1. Jun 10, 2009 #1


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    < preamble >
    Not sure if this belongs in physics, chemistry or engineering.

    I feel sort of silly, because I should know this. I'll probably do a face-palm when I get the answer.
    < /preamble >

    My pool has gotten cloudy so I've thrown some chlorine in. This killed the bacteria allowing the filter to remove it, and my pool is now clear.

    I know what the chlorine does; it causes the bacteria's cells to rupture, killing them.

    My question: What is it about exploded bacteria bits that allows the sand filter to sweep them up?

    My first hypothesis: The filter is actually not involved. Suspended bacteria are significant in size enough to cause cloudy water. Contrarily, dead bacteria dissolve into their comiponent parts (various gases, ions, salts) which, being much simpler molecules or even atoms, go into solution. As solutions, they are transparent. i.e. the components of the bacteria are still there (though now harmless), but they no longer affect the clarity of the water.
    Last edited: Jun 10, 2009
  2. jcsd
  3. Jun 10, 2009 #2
    Doesn't the filter charge consist of diatomaceous earth rather than sand?
  4. Jun 10, 2009 #3


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    Some are, some are not. http://www.haywardnet.com/inground/products/filters/Pro_Series_Top_Mount.cfm" [Broken].
    Last edited by a moderator: May 4, 2017
  5. Jun 11, 2009 #4


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    I thought it was more that if they are alive and multiplying, the filter can't keep up with the growth. If you kill them, then the filter just needs to handle the dead bodies and not all the growth.

    Usually it's algae that grows in pools and makes them visibly cloudy. If it were bacteria, that would be quite the toxic area if it was cloudy. :bugeye:
  6. Jun 11, 2009 #5
    You've got me wondering what sort or shapes the grains should be to best perform filtering. Both high porosity and places for debrit to cling or bond would seem to be important. Which would be best; sharp edged sand, or rounded? I think that diatoms would be very sharp. Or maybe it makes little difference.

    A magnifying glass could answer what kind you are using. There should be magnified pictures of sand on the net.

    ...So I pulled up a few.

    http://www.icbm.de/pmbio/mikrobiologischer-garten/pics/for02.jpg [Broken]




    Beautiful in magnification.
    Last edited by a moderator: May 4, 2017
  7. Jun 11, 2009 #6


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    I read just yesterday that, after ten years or so, "the edges have been worn off" the sand, so it should be replaced.

    I also found out that sand and diatomaceous earth are not interchangeable in a filter.
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