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Thread: New Sand in Sand Filters..... Turns Pool green for 3 days.

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    New Sand in Sand Filters..... Turns Pool green for 3 days.

    Hey it Shawn and iamcanadian lol. Our pool is a public facility with Main Pool 150000 gallons, Leisure Pool at 25000 gallons, two small Hot Tubs and sauna. I recently changed out the sand in Main Pool filter. (broken Lateral) As I put the filter back on line everything seemed good. The next morning the pool was green in color (normally blue). The pool was completely balanced and clear just green. It slowly cleared over 2-3 days back to it original color. Why? What? and can it be avoided next time?

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    Patrick_B's Avatar
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    Re: New Sand in Sand Filters..... Turns Pool green for 3 day

    Welcome to the forum.

    Without having more information, it will be difficult to answer you properly. New sand alone won't turn your water green.

    How long were you down for repairs?

    Can you give us some test result numbers and tell us how you are Chlorinating the pool? Also, does someone else help out with pool the pool Chemistry?

    Please share all the information you can so we are able to better answer your questions.
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    Re: New Sand in Sand Filters..... Turns Pool green for 3 day

    Did you add a considerable amount of fresh water during this changeover? Did you add a considerable amount of chlorine?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: New Sand in Sand Filters..... Turns Pool green for 3 day

    Hey , sorry its been so long hope your still around. Answers, We were down less than 4 hours, we run dual filters for main pool so we just took one off line and ran with the one filter til supplies had arrived. No large amount of fresh water or Cl2 was added as we were only down short time. Yes other people help out with water chemistry, we have two maintenance staff. hope that helps......

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    Patrick_B's Avatar
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    Re: New Sand in Sand Filters..... Turns Pool green for 3 day

    It is really difficult to say much without more info. If you can post a full set of test readings it might help. Especially if it happens again...please post them up.
    TFP Moderator
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    Re: New Sand in Sand Filters..... Turns Pool green for 3 days.

    This response is speculation but is based on observations in my pool.

    Here's what I believe is happening.......

    When you changed the sand, you introduced a small amount of iron in the pool. Whether that iron came from the sand or the source water or even something else I cannot say.

    Nevertheless, when the iron (still in solution) met with the chlorine in the pool, it precipitated that iron to a yellowish solid. Yellow solids mixed in with blue pool water makes green pool water.

    Now, because the iron has already precipitated to a solid, it is slowly being filtered out mechanically from your pool and in a few days, everything returns to normal.

    What little iron there was has been captured by your filter (for backwash later) or perhaps returns to suspension and remains in your pool.

    Again, I cannot answer how the iron got there and I cannot definitively say I am right......I have observed the same issue in my pool at start up most Springs.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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