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Thread: Chlorine and bather load

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    Chlorine and bather load

    I understand the target and min levels of chlorine but how do I determine if i need extra chlorine for bather load.
    Do I turn up the SWG before the party or after? Do I dose with liquid and how much? Last summer the water went cloudy after a few kids spent the afternoon in the pool. I think I may have had a low level algae problem even though the water was clear. As I remember the chlorine was 8-10 with cya at 60ish.

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    Richard320's Avatar
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    Re: Chlorine and bather load

    Quote Originally Posted by bribri
    I understand the target and min levels of chlorine but how do I determine if i need extra chlorine for bather load.
    Do I turn up the SWG before the party or after? Do I dose with liquid and how much? Last summer the water went cloudy after a few kids spent the afternoon in the pool. I think I may have had a low level algae problem even though the water was clear. As I remember the chlorine was 8-10 with cya at 60ish.
    Yes.

    Run an overnight loss test (be sure to turn the SWCG off for it) to be sure you have no algae problem.

    If I'm having a bunch of people in the pool, I'll dump in an extra quart or so (2 ppm) before they get there, and probably a half gallon after we're done. If I had a SWCG, I'd crank it up to max the whole time; it's safe to swim all the way to shock level, so there should be no problem.
    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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    Re: Chlorine and bather load

    Thanks, How many ppm per child? kidding. Ice just melted today in pool. Cool spring in Barrie Ontario

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    Re: Chlorine and bather load

    A rough rule-of-thumb is that the chlorine demand from bather load in swimming pools is around 4 grams of chlorine per person-hour. In a 7500 gallon pool, this is only 0.14 ppm FC per person-hour. This is why you mostly see chlorine loss from sunlight being the dominant factor and not notice much change when there are just a few swimmers in the pool. However, if you have a pool party and have 10 people in the pool, then 1.4 ppm FC per hour is significant and even in a larger pool the demand would be noticeable.

    Now if a child (or adult) urinates in the pool, then all bets are off since that's a much larger chlorine demand from one person. One cup of urine in 7500 gallons needs at least 0.8 ppm FC to oxidize it.

    So Richard's advice of just bumping up the FC level by 2 ppm or so is usually sufficient and you can always monitor the FC level afterwards to see if you need to raise it higher. With CYA in the water, having a higher FC is not unpleasant.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: Chlorine and bather load

    I knew something was up when those kid stayed in the water all afternoon. I wish I could get some of that red dye that would expose who was urinating in My pool. Thanks for the info.

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    linen's Avatar
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    Re: Chlorine and bather load

    Quote Originally Posted by bribri
    I wish I could get some of that red dye that would expose who was urinating in My pool.
    Urban legend
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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