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Thread: Am I using the calculator wrong? AM I missing something.

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    j_m_min's Avatar
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    Am I using the calculator wrong? AM I missing something.

    OK, I drained the pool. CYA was off charts. Now CYA

    Here are my numbers:

    FC 2.8
    CC 0
    PH 7.1
    CYA 35.
    TA is good
    CA is 100, so low. I have some Cal hypo shock, and I was going to buy some cal hypo chlorine to get that up.


    My pool isn't exactly square, it curves in and out, but is 33 ft long and 22 ft wide. 3 ft shallow end 6 ft deep, So I am assuming it is about 25,000 gallons. The calculator says 24,400.

    It has been 2 weeks since the drain and I was running the chlorinator with dichlor pucks to get the CYA up and had a bottle of liquid CYA.

    I input ph at 7.1. It says put in 129 oz of Borax.

    I input FC at 2.8. It says add 45 oz of 8.25% bleach to get 4 FC.

    I put in 75 oz of the Mule Borax, one box.
    I put in about 80 oz of 8.25 HEB store bleach.

    Next moring FC is 3.0. PH is 8.0 (or maybe higher).

    Am I using this caculator wrong?

    Is there some trick to getting FC up and staying up? At this rate I will be needing to put in a half a bottle of bleach everyday. Is this Normal? That is like $11.50 in bleach a week.

    Thanks for the help.
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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    Task's Avatar
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    Re: Am I using the calculator wrong? AM I missing something.

    I typically have to add about 2-3 cups of bleach each day to keep my FC up. My pool sounds like its a bit smaller then yours based on your 25,000 gallon estimate and I use 12.5% bleach so I guess that sounds about right.
    16'x32' Inground Vinyl, 21,100 gallons, Hayward 1.5 HP Super Pump, Hayward Pro Series S244T 3.1ft Sand Filter
    TFTestKits, Pool School, ABC's of Pool Water Chemistry, Chlorine/CYA Chart, PoolMath

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    Mod Squad JohnT's Avatar
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    Re: Am I using the calculator wrong? AM I missing something.

    Without knowing the TA, it would be hard to know what the pH is going to do. With zero TA, it only takes 23oz of borax to raise your pH that far. With 100ppm TA it shouldn't raise your pH much beyond 7.3.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Richard320's Avatar
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    Re: Am I using the calculator wrong? AM I missing something.

    Quote Originally Posted by j_m_min View Post
    OK, I drained the pool. CYA was off charts. Now CYA

    Here are my numbers:

    FC 2.8
    CC 0
    PH 7.1
    CYA 35.
    TA is good
    CA is 100, so low. I have some Cal hypo shock, and I was going to buy some cal hypo chlorine to get that up.


    My pool isn't exactly square, it curves in and out, but is 33 ft long and 22 ft wide. 3 ft shallow end 6 ft deep, So I am assuming it is about 25,000 gallons. The calculator says 24,400.

    It has been 2 weeks since the drain and I was running the chlorinator with dichlor pucks to get the CYA up and had a bottle of liquid CYA.

    I input ph at 7.1. It says put in 129 oz of Borax.

    I input FC at 2.8. It says add 45 oz of 8.25% bleach to get 4 FC.

    I put in 75 oz of the Mule Borax, one box.
    I put in about 80 oz of 8.25 HEB store bleach.

    Next moring FC is 3.0. PH is 8.0 (or maybe higher).

    Am I using this caculator wrong?

    Is there some trick to getting FC up and staying up? At this rate I will be needing to put in a half a bottle of bleach everyday. Is this Normal? That is like $11.50 in bleach a week.

    Thanks for the help.
    Yes, you are using poolmath incorrectly. To calculate pH adjustments, it asks for a number for TA. "Good" is not a valid number. You might also be wrong on your pool volume. It will take some time and observation to get that figured. If you consistently overshoot or undershoot on dosage, your pool is smaller or bigger than you thought. Shave two thousand gallons. If you start undershooting, add 1000. You'll get it figured out eventually.

    Also, chlorine is a consumable item. Shop for better prices. Sometimes pool stores sell higher strength bleach that works out cheaper than clorox. My 16000 gallon pool uses about a quart of 12.5% per day. Your pool is almost twice as big and your bleach is weaker, so half a jug sounds about right. It needs to be fed every day, whether it's by adding bleach or generating it in place with a saltwater chlorine generator.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Task's Avatar
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    Re: Am I using the calculator wrong? AM I missing something.

    Try seeing if a local pool store sells 12.5% liquid chlorine. I get mine from my pool builder. 5 gallons of 12.5% costs me about $14.
    16'x32' Inground Vinyl, 21,100 gallons, Hayward 1.5 HP Super Pump, Hayward Pro Series S244T 3.1ft Sand Filter
    TFTestKits, Pool School, ABC's of Pool Water Chemistry, Chlorine/CYA Chart, PoolMath

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    j_m_min's Avatar
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    Re: Am I using the calculator wrong? AM I missing something.

    I couldn't remember the TA number off the top of my head. Left the paper at home. It is 100.
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

  7. Back To Top    #7
    j_m_min's Avatar
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    Re: Am I using the calculator wrong? AM I missing something.

    Just curious how adding 75 oz instead of 129 oz of borax shot it up so high?
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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