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Thread: What happens to the chemicals?

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    Join Date
    Feb 2018
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    Savannah, GA
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    What happens to the chemicals?

    Okay, I have been reading about adjusting and maintaining correct balance in the water. Over time, as the pH, TA, etc. are adjusted, what happens to the chemicals added to make adjustments? Do they build up or precipitate out, or something else? After reading about CYA buildup, I am just wondering if other chemicals can become a problem.

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    JoyfulNoise's Avatar
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    May 2015
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    Re: What happens to the chemicals?

    Chlorine in chlorinating compounds (hypochlorite, dichlor, trichlor, cal-hypo) is reduced into chloride ion (Cl-) and measured as salt build up. All chlorinated swimming pools build up chloride ion over time. Muriatic acid (hydrogen chloride) also adds chloride ion to the water while dry acid (sodium bisulfate) leaves sulfate ions behind. Dichlor and trichlor add cyanuric acid as well as chlorine and cal-hypo adds calcium ions in the form of carbonates and hydroxides. Alkalinity increaser (aka, baking soda) and pHUp (soda ash or sodium carbonate) adds sodium ions and carbonates to the water. Sodium doesn't matter at all because it remains in solution and will not scale out at any normal pH. Carbonates and bicarbonates vary in concentration with dissolved CO2 and atmospheric CO2 depending on pH and the outgassing rate of CO2 from the pool to the atmosphere. All pool water is over-carbonated relative to atmospheric CO2 levels (think of the pool like an opened soda can) and so CO2 is constantly outgassing to the atmosphere. This is the reason why pH is always increasing in most pool water. Bathers leave behind salt from sweat and urine as well as organic compounds that breakdown from chlorine oxidation into simpler organics. Nitrates and phosphates build up over time and, while phosphates can be removed if the pool owner wants to do that, nitrates can not be removed and simply build up in the water.

    In my area of the country where water is scare and we try not to lose a lot of it out of our pools, pool's eventually need to be drained and refilled. In wetter climates where rain and winter snow is plentiful, there's enough water exchange to typically keep pool water balanced without any full draining required to removed dissolved solids and salts.

    Total dissolved solids (TDS) is the old test method pool operators used to determine the buildup of chemicals in pool water. However nowadays, with modern test kits, pool owners can test for each specific chemical level in water and know it's concentration rather than some unspecific total value.
    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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    Feb 2018
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    Savannah, GA
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    Re: What happens to the chemicals?

    Thanks for the info. We average about 48" of rainfall a year here, so I guess it should not be a problem.

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    cfherrman's Avatar
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    May 2017
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    Re: What happens to the chemicals?

    Take a look at pool math's "effects of adding chemicals" at the bottom, show how much salt and other effects. Knowing what exactly happens when you add a chemical is a key part of tfpc
    Casey
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