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Thread: Shocking and water below 60 degrees

  1. Back To Top    #1

    Join Date
    Aug 2009
    Raleigh, NC

    Shocking and water below 60 degrees

    In the pool closing sticky it states the following:

    "Two or three days before closing, I bring the pool up to shock level and hold it there until FC holds overnight (which it generally does right off on the first night). Then I let the chlorine level fall about half way back to normal levels, typically another day and a half."

    There seems to be a contradiction in this statement because I don't believe it will drop that fast in water below 60 degrees. Currently my water temperature is 66 degrees. I maintain my chlorine in the 4-9 range and it took 3 days to drop from 9 to 4. I'm waiting to close my pool and my TFP calculator suggested shock level is 22. The problem is that finding a day this time of year when the level has dropped to about 11 and the weather is conducive to closing the pool becomes a low probability gamble, i.e. the level could be too high, most likely, or too low less likely.

    I recall several years ago that it was late November and my CL levels were still close to shock values so I closed it anyway because the weather forecast for the next few weeks was miserable. When I uncovered the pool the bottom of the cover was bleached out. The liner was as well but it didn't have much if any color left in it anyway. However, I have a new liner that I donít want to get bleached.
    The weather has been fairly warm so far and has had few nights below 50 and many days over 70 with a lot of overcast rainy days but that can change in a heartbeat. 3 or 4 nights in the 30s and highs in the 50s an that water temperature will drop rapidly but the CL level wonít.
    My questions:
    1. I have had no algae all year and no signs of any so is it really necessary to shock the pool or is just closing it at normal levels a fairly safe option?
    2. Is 66 degrees that big of a risk for algae growth compared to 60?
    3. Would closing the pool at or near shock level bleach my pool liner?

    Thanks for any responses.
    25,000 gallon inground vinyl sand filter 60 gpm 1 hp pump

  2. Back To Top    #2

    Join Date
    Jul 2014
    Hope Mills, NC

    Re: Shocking and water below 60 degrees

    My chlorine was at 22 when I closed this year. I'm not worried, 22 is high, but not horrible, bleaching high. It will be 0 in April.
    16 x 32 17500 gallons
    Vinyl in-ground
    Hayward 250# Sand Filter
    1 HP Pump
    Hayward SWG

  3. Back To Top    #3

    Join Date
    Aug 2014
    Shallotte, NC

    Re: Shocking and water below 60 degrees

    Y'all are closing early! My pool is still 69- 72 degrees.....

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