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Thread: Reverse Math to determine Pool Size

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    Join Date
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    Reverse Math to determine Pool Size

    Greetings all!

    Inherited a pool that came with the house - is there a way to reverse calculate the pools volume based upon affect of a predetermined amount of chemicals?

    For example, wait until night, turn SWG off, test, add 40 oz of 10% liquid bleach and test again in 30 minutes? I know and use the pool calculator but don't see a way (or the math) to reverse the calcs.

    Thanks!
    ~26,000 gal (still dialing it in) / in-ground saltwater (Hayward T-CELL-15) / Blue Granite PebbleSheen / 2hp WhisperFlo pumps (main), 1.5hp WhisperFlo pump (waterfall) / Pentair DE filter / AquaLogic control / Polaris cleaner aka "Trackie" / Dallas, TX

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    JoyfulNoise's Avatar
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    Re: Reverse Math to determine Pool Size

    Maybe this suggestion is too much work but wouldn't the county or municipality you live in have records of the house and the pool build? My county (Pima County, AZ) wanted all details of the pool build submitted. I think there's even online records for the build details.

    Just a thought in case you wanted an exact number.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Divin Dave's Avatar
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    Re: Reverse Math to determine Pool Size

    Using pool math, you can use "the effects of adding" towards the bottom and use what you think your pool volume is, then add and test. If you are a tad higher or lower than what you should be, then adjust the volume accordingly.

    Chlorine isnt going to work out very well. Chlorine looses a bit of potency with age. Entirely possible that if it says 10% on the bottle, its actually 9.5, which would skew the test results.

    pH would be better.

    If you really want to so have some fun though, you can calculate it chemically by the directions in this thread and get pretty close. I did it. Its interesting to do.
    A Chemical Way of Calculating Pool Volume
    Divin Dave,
    IG Vinyl, 15' x 30', 3 1/2' - 6' deep, Oval, ~15K gal, Intelliclor IC40, Intelliflo VS pump, Clean and Clear 420 Filter, auto-fill-disabled, Retrofit LED Color Light, Dolphin Nautilus Robot, TF100 Test Kit, Taylor K1766 Salt Test Kit, Tftestkit Pressure Gauge.
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    Re: Reverse Math to determine Pool Size

    Thanks JoyfulNoise, hadn't thought of that!

    Dave, thanks this is fascinating. Is there a drop test for Ph I should be using? I only have that 2 sided CL/Ph tester thing (I'm sure it has a name) but also use the powder/drops to test Cl.

    I like the idea of the thread you sent me though, I'm going to outsource this to my brother in law who has a masters in chemical engineering and my boy scout who is 11. I'm sure there is a merit badge about chemistry in there somewhere!
    ~26,000 gal (still dialing it in) / in-ground saltwater (Hayward T-CELL-15) / Blue Granite PebbleSheen / 2hp WhisperFlo pumps (main), 1.5hp WhisperFlo pump (waterfall) / Pentair DE filter / AquaLogic control / Polaris cleaner aka "Trackie" / Dallas, TX

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    AprilsZoo's Avatar
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    Re: Reverse Math to determine Pool Size

    Quote Originally Posted by muffin_dad View Post

    Dave, thanks this is fascinating. Is there a drop test for Ph I should be using? I only have that 2 sided CL/Ph tester thing (I'm sure it has a name) but also use the powder/drops to test Cl.
    The Phenol Red pH test you have is the only drops-based test I'm aware of.

    All the various Yellow/Red type kits out there use the OTO reagent for Cl, and the Phenol Red (in differing concentrations) for pH.

    The "2-sided testing thing" does have a name... It is usually called a "Comparator block" or just a "Comparator".

    For pH it is important to replace the reagent (when you run out) with one of the right concentration. And probably best to stick with the same manufacturer/brand.

    But the OTO seems to be pretty standard, even across brands.
    That makes it easier to find reagent, if like me--you find out that you are running low only once it is totally gone... requiring a hurried run to the store, so your teenager can do his job, because he isn't allowed to swim unless he tests Cl and pH first.


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    Mod Squad Bama Rambler's Avatar
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    Re: Reverse Math to determine Pool Size

    A lot of us have used PoolMath to adjust the volume for pools. Dave outlined how to do it. I'll only add that you should run the test many times with different chemicals before settling on a volume. Over time you'll find out that you will get pretty close to the 'real' volume this way.
    Dave J. TFP Moderator
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