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Thread: Closing FC Level - Shock or 50% Shock?

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    Closing FC Level - Shock or 50% Shock?

    Closing the pool this coming weekend and currently have the FC at shock level. The pool school in-ground closing instructions say to let the FC fall back down to about 50% shock level before closing. Why wait for it to drop? Seems like a higher FC level would be a good thing to help the chlorine last through the winter. What do others do?
    Free-form concrete walls with vinyl liner, 18,000 gallon capacity, Jandy 1.5HP e-Pump, Jandy DEV48 DE filter (using cellulose media), Jandy AE2500 heat pump, Jandy Aqualink Power Center with 14-blade cell kit and Jandy PDA-P8 wireless control system.

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    Mod Squad jblizzle's Avatar
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    Re: Closing FC Level - Shock or 50% Shock?

    Doesn't it say to let it drop before adding poly 60? If you are not adding the poly, then you should be fine to close I think.

    .... maybe I should go read the articles again since I never experience this so called closing
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    Re: Closing FC Level - Shock or 50% Shock?

    I don't understand the purpose of letting the FC drop to 50% prior to adding Poly60. I know that Poly60 has a chlorine demand but can't understand why we should let the FC drop prior to adding Poly60 and then have to add more bleach to bring the FC back up again.

    I don't plan on using Poly60 this year but want to understand what the reasoning is behind the instructions. Also, is there any reason that I shouldn't close the pool at shock level?
    Free-form concrete walls with vinyl liner, 18,000 gallon capacity, Jandy 1.5HP e-Pump, Jandy DEV48 DE filter (using cellulose media), Jandy AE2500 heat pump, Jandy Aqualink Power Center with 14-blade cell kit and Jandy PDA-P8 wireless control system.

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    Smykowski's Avatar
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    Re: Closing FC Level - Shock or 50% Shock?

    I think it has something to do with the demand o the chlorine by the polyquat. If the FC is higher and you add the poly, the poly gets oxidized much more quickly.

    That's a best guess from what I remember reading. I could also be completely off base.

    I bring my pool up to shock level (or slightly above), no algaecide, and cover it up.
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    Re: Closing FC Level - Shock or 50% Shock?

    Thanks. That's what I plan on doing. I just like to know that I will not damage the liner or my Looploc mesh cover with the FC at shock level.
    Free-form concrete walls with vinyl liner, 18,000 gallon capacity, Jandy 1.5HP e-Pump, Jandy DEV48 DE filter (using cellulose media), Jandy AE2500 heat pump, Jandy Aqualink Power Center with 14-blade cell kit and Jandy PDA-P8 wireless control system.

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    Re: Closing FC Level - Shock or 50% Shock?

    I had to artificially increase my FC with bleach to shock levels to close because my SWG quit working due to low temp. But I got up to shock levels. Added my algaecide and closed the autocover.


    30x20 vinyl IG, Hayward SD60 with Pentair Dynamo 340219 2HP pump, Compupool CPSC24 SWG, Hayward H200FDN heater. APC automatic pool cover.
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