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Thread: Shock and High pH

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    Shock and High pH

    Good morning,

    Was away for a few days and returned to find a hazy green pool -- bad timing as we really need the relief during this blistering heat.

    I shocked with bleach last night -- was shooting for 15.0 fc but hit 18.0 fc. The pH was a little high at 7.8, so I also added a couple of pounds of dry acid.

    Checked this morning and we are at 15.0 fc, but the pH is reading 8.0+! It is a 30k gallon in-ground vinyl pool. Numbers pre-shock:

    FC: 1.0
    Alk: 110
    pH: 7.8
    CYA: 30-35

    Post shock:
    FC: 15.0
    pH: 8.0+

    Should I try to adjust the pH now, or wait until FC comes down? Also, what would be a safe FC level to allow swimming -- kids are hot and want to go swimming!!

    Thanks very much for your thoughts.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

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    aa62579's Avatar
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    Re: Shock and High pH

    Your pH test will be off when you have high level of FC. Don't worry about it until you are done shocking and your FC level has come down under 10. Remember, shocking is not a one time thing!
    ~~ Allison ~~
    Intex 18' x 48" Easy Set Pool, approximately 5455 gallons
    Krystal Clear 1500 GPH Filter Pump Model 56635EG - 635 with Auto Timer
    BBB FOR BEGINNERS ~ THIS IS A MUST READ FOR ANYONE OVERWHELMED!!

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    Re: Shock and High pH

    Ditto that excellent post from aa62579!!
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Shock and High pH

    Thanks to you both! How long do I need to keep a steady shock level before allowing it to drop, and what would be a safe FC level for return to swimming?
    Thanks.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

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    dattia's Avatar
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    Re: Shock and High pH

    You need to remain in the shock process until the organics in your water have been killed off. The three criteria for a completed process are passing the Overnight Chlorine Loss Test, having a CC level of .5 or less and crystal clear water. I am assuming that you have a decent test kit. According to the CYA/Chlorine Chart in Pool School the shock level for CYA 30 is 12 and for CYA 40 is 16, so you are in the ballpark there. Minimum FC to maintain after shocking would be 3 and your Target FC would be 5 (basing that on CYA 40). The general consensus around here is that you can swim up to your shock level, but not higher.
    27' round AG
    Hayward Matrix 1 1/2 HP Pump
    Hayward S210T Sand Filter

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    Re: Shock and High pH

    Thanks very much. Just checked numbers again:

    FC: 14.5
    CC: 0.0
    Alk: 110
    pH: 8

    Pool is half-shaded and blue/green cloudy, and my daughter is hanging over my shoulder, saying "when?!"

    So we can enter the pool with FC between 3 and 12?
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

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    aa62579's Avatar
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    Re: Shock and High pH

    Yes, but don't let your chlorine drop to that level until you have successfully completed the shocking process. Until your pool is clear (and you have passed the other two tests), you do not need to let your FC level drop below shock level. Make sure you have your filter running 24/7 to help clear things up.
    ~~ Allison ~~
    Intex 18' x 48" Easy Set Pool, approximately 5455 gallons
    Krystal Clear 1500 GPH Filter Pump Model 56635EG - 635 with Auto Timer
    BBB FOR BEGINNERS ~ THIS IS A MUST READ FOR ANYONE OVERWHELMED!!

  8. Back To Top    #8

    Re: Shock and High pH

    Thanks Allison. Will check levels in an hour when the sun goes off the pool, add bleach if necessary, and check again in the morning to see what the overnight FC is. I can see the bottom of the deep end, but still pretty cloudy. 90+ degrees -- I want to beat this algae!
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  9. Back To Top    #9

    Re: Shock and High pH

    No swimming until shock is done. Very hard on tender skin; eyes, nose, privates.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    Re: Shock and High pH

    Will check levels in an hour when the sun goes off the pool, add bleach if necessary, and check again in the morning to see what the overnight FC is.
    That will not give you correct results. You must not add chlorine IN BETWEEN your evening test and your AM test. There is an article in Pool School that describes the OCLT.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  11. Back To Top    #11
    aa62579's Avatar
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    Re: Shock and High pH

    Quote Originally Posted by poolman10
    Thanks Allison. Will check levels in an hour when the sun goes off the pool, add bleach if necessary, and check again in the morning to see what the overnight FC is. I can see the bottom of the deep end, but still pretty cloudy. 90+ degrees -- I want to beat this algae!
    If your pool water is not clear, there doesn't seem to be any reason to try to perform an OCLT unless you are just curious. Instead, I would try to test the chlorine multiple times tonight (hourly if possible) and keep adding bleach to keep it at shock level.

    If you are curious about the OCLT, wait about 30-45 minutes after your last chlorine addition and take a reading. Then take a reading in the morning before the sun comes up.
    ~~ Allison ~~
    Intex 18' x 48" Easy Set Pool, approximately 5455 gallons
    Krystal Clear 1500 GPH Filter Pump Model 56635EG - 635 with Auto Timer
    BBB FOR BEGINNERS ~ THIS IS A MUST READ FOR ANYONE OVERWHELMED!!

  12. Back To Top    #12

    Re: Shock and High pH

    Thanks for your comments.

    Dave -- I'm a knucklehead -- of course I'll can't drop bleach between readings. Thanks for reminding me.

    Allison -- good point. I was at 8.5 FC after the sun went off the pool. Brushed the pool, added some bleach, and now off to pick up some more bleach at Walmart.

    Thanks.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  13. Back To Top    #13

    Re: Shock and High pH

    FC at about 15 after sunset last night -- 14 this morning. Green/blue haze is now a very, very light haze. Keep the shock up?

    Thanks, all, for your help.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  14. Back To Top    #14

    Re: Shock and High pH

    Do you have any CC on test? If above 0.5 CC, keep shocking.

    Also, brush, and check filter and skimmers.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

  15. Back To Top    #15

    Re: Shock and High pH

    Just checked the numbers and no CC at this time. FC is down to 9 after 2.5 hours in the sun. Does that seem like a big drop? Is my CYA ok at 30-35?
    Thanks.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

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