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Thread: Following pool calc precisely with wild chem swing results

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    Following pool calc precisely with wild chem swing results

    I have measured my pool twice and used the pool calculator to determine the gallons. I have come up with 21,400 gallons. I follow the instructions on the pool calculator to a T, but I keep having wild swings in my chemistry after putting in the prescribed amounts. For example, yesterday I needed to lower my pH from 7.8 to 7.2. With a TA of 210, the pool calculator said to add 105 oz of muriatic acid-which I did. Then I ended up with a pH at 6.8 (or possibly lower because 6.8 is the lowest reading I have). Then I had to add borax to raise the pH back to 7.2 so I could do my AA treatment.

    This sort of thing has happened repeatedly, and I am blowing through products like crazy. What am I doing wrong???

    Thanks for taking a look-Stephani
    16.8k gallons, IG fiberglass (installed approximately 2000), 1 HP Challenger Pentair pump, Hayward SwimClear cartridge filter (none of the particulars are marked, but it has four 100 sq ft cartridges), UltraPure oxidizer, TF-100 test kit

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    Richard320's Avatar
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    Re: Following pool calc precisely with wild chem swing resul

    You're overdosing. Which means you're doing the test wrong or the pool isn't as big as you think. Since the problem is consistent, it's most likely the volume.

    Try using 20,000 as the volume. Pay attention to pH changes and TA changes and see if the results match. If you still overdose, try 19000. At some point you will be underdosing, and you start adding back a few hundred at a time. Keeping a log and using "effects of adding chemicals" on Pool Calculator should have you dialed in within two or three weeks.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: Following pool calc precisely with wild chem swing resul

    That sounds like a good plan. I thought the depth might have been off, but I measured it again last night. It is 7' deep.

    I'll back off and see what happens. Thank you!
    16.8k gallons, IG fiberglass (installed approximately 2000), 1 HP Challenger Pentair pump, Hayward SwimClear cartridge filter (none of the particulars are marked, but it has four 100 sq ft cartridges), UltraPure oxidizer, TF-100 test kit

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    Re: Following pool calc precisely with wild chem swing resul

    Oh my gosh! Oh my gosh! Oh my gosh! I know what it is. The pool has two sunning ledges in the deep end. That has to be throwing it off!
    16.8k gallons, IG fiberglass (installed approximately 2000), 1 HP Challenger Pentair pump, Hayward SwimClear cartridge filter (none of the particulars are marked, but it has four 100 sq ft cartridges), UltraPure oxidizer, TF-100 test kit

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    Mod Squad woodyp's Avatar
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    Re: Following pool calc precisely with wild chem swing resul

    Another hint: Measure from the bottom of the pool to the middle of the skimmer where you normally keep your water level. NOT to the top of the tile or whatever.
    A 2" difference from the top of my skimmer to the middle is almost 700 gallons in my pool.
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    Re: Following pool calc precisely with wild chem swing resul

    Wow! Thanks, woodyp.
    16.8k gallons, IG fiberglass (installed approximately 2000), 1 HP Challenger Pentair pump, Hayward SwimClear cartridge filter (none of the particulars are marked, but it has four 100 sq ft cartridges), UltraPure oxidizer, TF-100 test kit

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    Re: Following pool calc precisely with wild chem swing resul

    Don't forget to calculate the depth as an average depth. If you are using 7' deep for the depth you are probably off by quite a bit. If your shallow end is 3.5' deep and the deep end is 7', use 5' for your depth of pool.
    16k gal plaster with raised spa, Jandy DEV60 filter, 2 HP 2-speed SHPF Jandy Stealth pump
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    Re: Following pool calc precisely with wild chem swing resul

    Crud! I did that too! No wonder everything has been off.
    16.8k gallons, IG fiberglass (installed approximately 2000), 1 HP Challenger Pentair pump, Hayward SwimClear cartridge filter (none of the particulars are marked, but it has four 100 sq ft cartridges), UltraPure oxidizer, TF-100 test kit

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