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Thread: Effect of hot water temperature on chlorine consumption?

  1. #1
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    Effect of hot water temperature on chlorine consumption?

    A little background: my pool gets FULL sun at least 12 hours a day and we've been near 100 for the past month, so the pool water temp is staying well above 90.

    I didn't stay on top of the pool for a couple of days last week, and inevitably I saw the signs of algae starting. I'm not sure if its green or algae, but the yellowish tint of the clouds when brushing tells me that it was mustard.

    So, now I'm trying to shock, but the chlorine levels are bottoming out within hours like I've never seen before.

    Example:

    8pm FC: 27
    10pm FC: 17
    7am FC: 2


    I always bump it back up, but I honestly can't afford to dump 10-15 gallons of chlorine in a day to keep the shock level up.

    I don't have CC when I test, so normally I'd assume that the pool is shocked. However, the water still isn't as clear as it should be and the FC readings would NORMALLY indicate that something is eating the chlorine.

    But, with the water temp still above 90 even after sitting all night, could that be why I can't keep it at shock levels?
    Pool Specs: 18x36 (~ 24,000 gal) IG vinyl w/ chlorinated water and 75 GPM sand filter with a 1 HP pump.

  2. #2
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    Re: Effect of hot water temperature on chlorine consumption?

    But, with the water temp still above 90 even after sitting all night, could that be why I can't keep it at shock levels?
    No. The problem is the algae (organics that remain in your pool)

    Unless you bring your FC up to shock level and HOLD IT THERE until your pool clears, (You are not holding chlorine up where it needs to be) you will forever be living with a green pool or forever loading it with chlorine until you get your mind set on shocking it continuously until it clears. Your FC consumption will drop down to normal as soon as you kill the organics.
    Dave S.
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  3. #3
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    Re: Effect of hot water temperature on chlorine consumption?

    You should post a full set of water test results. There may be something else going on that is interfering with the shocking process.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Effect of hot water temperature on chlorine consumption?

    Everything else is normal.

    pH: 7.6
    FC: 4.0
    CC: 0
    TC: 4.0
    TA: 150
    CYA: 55
    CH: I don't test for it because I have a vinyl, but this isn't the problem.

    I know how to shock and I've never had to put this much in.

    I thought I saw somewhere that mustard algae requires a much higher FC level, sometimes north of 40 or 50? If that's the case, I'll just get some sodium bromide and deal with the copper content later.
    Pool Specs: 18x36 (~ 24,000 gal) IG vinyl w/ chlorinated water and 75 GPM sand filter with a 1 HP pump.

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    Administrator JasonLion's Avatar
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    Re: Effect of hot water temperature on chlorine consumption?

    Your levels look good, except for the low FC level. The more frequently you can add chlorine, the sooner this will all be over. If you allow pauses where the FC level drops down, the algae starts growing back and then you will need yet more chlorine to deal with the new algae.

    Warm water speeds the rate at which algae grows.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  6. #6
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    Re: Effect of hot water temperature on chlorine consumption?

    Quote Originally Posted by JasonLion
    The more frequently you can add chlorine, the sooner this will all be over. If you allow pauses where the FC level drops down, the algae starts growing back and then you will need yet more chlorine to deal with the new algae.
    I understand the concept, just wondering if temperature affects chlorine consumption. Thanks for your time.
    Pool Specs: 18x36 (~ 24,000 gal) IG vinyl w/ chlorinated water and 75 GPM sand filter with a 1 HP pump.

  7. #7
    Administrator JasonLion's Avatar
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    Re: Effect of hot water temperature on chlorine consumption?

    During the day, warm water increases chlorine use. At night the the FC level should remain the same (ie no chlorine used up) regardless of temperature (assuming you don't have algae or some other organic contamination).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  8. #8
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    Re: Effect of hot water temperature on chlorine consumption?

    The problem is that the water temperature never drops more than a degree or two.

    Its sitting pretty at 95 right now and won't go below 92 before morning.

    EDIT: For the record, I understand that sunlight consumes/destroys chlorine. That's not the question I'm asking.
    Pool Specs: 18x36 (~ 24,000 gal) IG vinyl w/ chlorinated water and 75 GPM sand filter with a 1 HP pump.

  9. #9
    Administrator JasonLion's Avatar
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    Re: Effect of hot water temperature on chlorine consumption?

    Then I don't have any idea what you are asking.

    Your first post appeared to show a dramatic FC loss at night. That would not be caused by the water being warm. That is caused by something organic in your water that the chlorine is breaking down. Whatever is happening, it is not being caused by the water being warm, though warm water might be aggravating it. For example, if you have algae, your problem would be that you have algae, not that the water is warm. Now algae grows more quickly in warm water, so it will take more total chlorine to kill the algae than it would in cold water. But the warm water would not be what is causing the problem in the first place, the algae would be.

    Sunlight uses up more chorine when the water is warm than it does when the water is colder.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  10. #10
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    Re: Effect of hot water temperature on chlorine consumption?

    I am not sure what the question is, either.
    Dave S.
    Site Owner 42k vinyl and concrete pool, 1.5hp pump, 140gpm filter, No SWG
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  11. #11
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    Re: Effect of hot water temperature on chlorine consumption?

    How long are you running your pump and when are you running it?

    gg=alice
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  12. #12
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    Re: Effect of hot water temperature on chlorine consumption?

    The title of the thread is "Effect of hot water temperature on chlorine consumption". It appears to me that he is asking if hot water consumes chlorine. While he states that he does (did) have algae, it appears that he is questioning if hot water itself has any affect on chlorine consumption, and, if so, to what extent.

    Did I get that right, LongbowFoSho? Just trying to help you get an answer

  13. #13
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    Re: Effect of hot water temperature on chlorine consumption?

    You nailed it and I simultaneously understand what Jason is saying, lol.

    So basically, the temp of the water itself doesn't affect chlorine consumption, but it DOES promote faster algae growth which, in turn, consumes more chlorine.

    So I guess water temperature does affect chlorine consumption, but only indirectly through the promotion of accelerated algae growth.

    Without an organic in the water, the temp could be 100 and should theoretically have the same chlorine consumption rate as 80 degree water.

    I get it. Thanks for the help, guys.
    Pool Specs: 18x36 (~ 24,000 gal) IG vinyl w/ chlorinated water and 75 GPM sand filter with a 1 HP pump.

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