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Thread: Ph dropping when shocking

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    Ph dropping when shocking

    I'am shocking my pool to clear up cloudiness and I notice when I shock that my ph drops to about 7. I thought that it was suppose to rise when you have high chlorine levels
    18 X 40, Ig vinyl, 3/4 HP Sta-Rite Pump, Sta-rite System 3 Cartridge Filter, Sta-rite Gas Heater,
    Autopilot Ditigal SWG, Legend Pressure Side Pool Cleaner w/booster pump, TF100 Tester

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    Join Date
    Jul 2011
    Location
    St. Paul, MN
    Posts
    244

    Re: Ph dropping when shocking

    What type of chlorine are you using while shocking your pool? Can you post a full set of test results?
    20'x40' Oval 27,000 gallon Vinyl IG, Coverstar Auto Cover
    Hayward MaxFlo SP2303VSP, Sta-Rite PLD50 30 sq. ft. DE filter
    Rheem 266,000 btu natural gas heater
    Dolphin Nautilus Plus with Clever Clean
    TF-100 testkit w/ Speed Stir

  3. Back To Top    #3

    Re: Ph dropping when shocking

    Liquid 10% chlorine.
    Fc=23
    Cc=0
    Cya=90
    Ph=7.0-7.2
    Ta=110
    Ch=230
    Salt=3100
    18 X 40, Ig vinyl, 3/4 HP Sta-Rite Pump, Sta-rite System 3 Cartridge Filter, Sta-rite Gas Heater,
    Autopilot Ditigal SWG, Legend Pressure Side Pool Cleaner w/booster pump, TF100 Tester

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    Join Date
    Jun 2011
    Location
    Northeast Ohio USA
    Posts
    178

    Re: Ph dropping when shocking

    They say that pH reads higher than it is at high FC levels. I think that is more because the test is skewed, than the pH actually rising in the water, but I could be wrong. In any case, I never noticed a rise in pH when I was shocking, more like a decrease if anything, similar to what you are suggesting.

    Your TA and CYA are a little higher than recommended (TA moreso). which might lead to a natural lowering trend in pH, but again I am guessing.

    I would monitor it, and if it drops further, take action to adjust it back to 7.2. Check again at normal FC levels (once shocking process is complete), and adjust again as necessary (back to normal 7.5-7.8 level for swimming)
    Vinyl In-Ground (vinyl) - about 21600 gallons (18x32 Grecian)
    Hayward DE (model 7220?) filter with Multiport valve
    Challenger Hi Flo Pump (3/4 HP)
    Intex SWG
    leaky/non-functioning Raypak Versa Natural Gas Heater *removed*

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    Re: Ph dropping when shocking

    pH won't be accurate when the FC is over 10 ppm. What was the pH before adding the liquid chlorine?

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    Re: Ph dropping when shocking

    It is possible that your chlorine in bleaching out your pH indicator. Does your test kit have you adding chlorine neutralizer? Is your chlorine level above 10 ppm?
    8 lane 25 meter 200,000 gallon outdoor pool (liquid chlorine)
    3 lane 25 yard 60,000 gallon indoor pool (liquid chlorine)
    3 Spa's 1200-600 gallon (trichlor/liquid chlorine)
    1 kids pool 40,000 gallon
    14x24 above ground SWG
    44,000 inground home pool (trichlor/liquid chrloine)
    AFO/CPO/LGIT/WSIT
    Southwest Utah Health Inspector/Pool Regulator

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    Join Date
    Nov 2010
    Location
    Calera, Al
    Posts
    271

    Re: Ph dropping when shocking

    Quote Originally Posted by JamesW
    pH won't be accurate when the FC is over 10 ppm. What was the pH before adding the liquid chlorine?
    x2
    17,000 gal, IG Gunite Diamond Brite plaster Kidneybean,w/7x11 tanning ledge& 3x5 swimout bench,244T 300lb Hayward Pro high rate sand filter(63 GPM) , Hayward 1Hp Super Pump w/3/4 hp booster pump, Polaris 280, Laars Lite 2 175k N/G Heater, Tf-100, Speed stir

  8. Back To Top    #8

    Re: Ph dropping when shocking

    I'am using the TF-100 test kit. My ph was 7.5-7.8 before shocking.
    18 X 40, Ig vinyl, 3/4 HP Sta-Rite Pump, Sta-rite System 3 Cartridge Filter, Sta-rite Gas Heater,
    Autopilot Ditigal SWG, Legend Pressure Side Pool Cleaner w/booster pump, TF100 Tester

  9. Back To Top    #9

    Re: Ph dropping when shocking

    pH won't drop when adding liquid chlorine, it will rise a little bit. Don't rely on pH testing when the FC is over 10 ppm.

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