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Thread: Losing a lot of chlorine during the day

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    Losing a lot of chlorine during the day

    My pool is in direct sunlight practically from dawn till dusk. Here where I live the temps are holding at about 105-107 F all day. I've been using liquid chlorine for months now and have gotten used to daily doses. Back in the winter I was using roughly 32 oz. per day when I was trying to maintain around 1.5-2 PPM FC. I found out that THOSE numbers were too low considering my CYA level of 35-40 and was told that higher FC was not only recommended but was safer than keeping the FC at 1.5-2.

    I've attempted to keep my FC levels at about 4PPM now for about a month and a half and my small algae pockets have started to dissipate. I've also been scrubbing them manually.

    My new problem/question that has arisen is this. I am now adding 186 oz.'s of bleach per day and it is still not enough by the end of the day to have maintained a level of 4PPM. As a matter of fact, by the end of the day the FC levels are back down to 1-2 range.

    I've been testing in the morning before the sun is high and hot and I read around 4-5 PPM. But after the sun has gone mostly down and but there is still light in the sky I test again and read about 1-2. Sometimes maybe even less than that.

    My CYA level again is at about 35-40 using the TF-100 kit that I bought. My questions is......is this amount of chlorine burn off normal and expected given the weather conditions I live in and the fact that the pool has full sun all day? If not normal, where am I wrong. Elevating CYA any higher would just require more chlorine anyway so as to make up for the loss in effectiveness by adding more CYA right?
    18,000 Gallons plaster, in ground. Pentair quad cartridge filter system charged w/DE. Built in the early 70's. Location: Bakersfield California. Summer temps from early May to late September, up into the 100'sF. Very low shade over pool, not until LATE evening. Palm tree drops pods from neighbors yard.

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    dattia's Avatar
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    Re: Losing a lot of chlorine during the day

    If you still have algae, have you shocked your pool according to the instructions in pool school? If you have organics in your pool, they will also consume your FC, so it may not be all sun. Do you have any CC's when testing the water?
    27' round AG
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    Butterfly's Avatar
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    Re: Losing a lot of chlorine during the day

    Please post a full set of test results.

    You have visible algae pockets and are using about 5ppm FC daily, you need to shock.

    Once you have completed the shock process (see red lines in my sig) you should raise your CYA up to about 50 and see how that holds your chlorine.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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    Re: Losing a lot of chlorine during the day

    As mentioned above, if you have visible algae, shocking the pool should be your first priority.

    Your FC loss is normal given your conditions.

    I would up the CYA to 50 for that pool and run FC 4-6ppm. I'll bet you lose a little less although it is not as predictable as one would hope.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Losing a lot of chlorine during the day

    Ah, forgot to mention that test results show VERY little IF ANY CC's. That should have been part of the initial post to help you understand just how much I'm losing to the sun. This is adding up man. Anyway, shocking pool should be the next step according to what I read. I will consult the pool school shock instructions. But yes, small algae pockets have been in my pool for months now. I scrub them away, try my best to keep the FC at around 4 PPM but they persist. It is however beginning to take them longer and longer before they come back.

    Just seeing that yellow test container be such a dark yellow worries me. I just don't want my kids swimming in water that's "too hot" with chorine. But I understand that the CYA level mitigates FC levels and so 4-6 PPM FC isn't too bad for them.

    Test results as of last night at 7 p.m. were this

    FC 1-1.5
    CC 0
    TA 110
    PH 7.8
    CYA 35

    Tested however in the morning before the sun went nuts and was at about FC 4 PPM.
    18,000 Gallons plaster, in ground. Pentair quad cartridge filter system charged w/DE. Built in the early 70's. Location: Bakersfield California. Summer temps from early May to late September, up into the 100'sF. Very low shade over pool, not until LATE evening. Palm tree drops pods from neighbors yard.

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    Re: Losing a lot of chlorine during the day

    I just don't want my kids swimming in water that's "too hot" with chorine.
    I know you don't swim in it, but when you add Clorox to an automatic washing machine, the FC is up around 300ppm and there is absolutely no CYA to buffer it.......yet no warning label whatsoever on the bottle of Clorox or on the machine.

    The tiny ppm's we deal with in pools is pretty darn safe especially when you factor in the buffering action of CYA.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    frogabog's Avatar
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    Re: Losing a lot of chlorine during the day

    With a CYA of 35 you should be dosing to 7ppm at night, which should leave you with 3-4ppm at the end of the day. It looks to me like you aren't quite hitting target. Loosing 50% of your chlorine every day is what's supposed to happen. To maintain minimum, you have to add enough every night so that loosing half the next day leaves you back at minimum.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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    Re: Losing a lot of chlorine during the day

    Quote Originally Posted by frogabog
    With a CYA of 35 you should be dosing to 7ppm at night, which should leave you with 3-4ppm at the end of the day. It looks to me like you aren't quite hitting target. Loosing 50% of your chlorine every day is what's supposed to happen. To maintain minimum, you have to add enough every night so that loosing half the next day leaves you back at minimum.

    This just occured to me tonight while I was dosing the pool. Stupid me has not been taking into consideration that I should be overdosing during the night so that the levels never drop below the minimum during the day.

    Here's what happened the past 24 hours.

    Raised FC levels to 13 last night. It was all the bleach I had on hand even though the chlorine/CYA chart said I should be at 16. Pool sat overnight at that level. I was unable to check the levels this morning due to Sunday activities elsewhere, and only was able to check them at about 2:30 this afternoon. At that point the FC was 7. So I lost 6 ppm during over night and during the day. I have noticed that when taking the morning readings and comparing them to evening readings I am indeed losing about 3-4 ppm during the day, presumably from just sunlight.

    So......the pool shock page in pool school and one of the mod's sigs in the posts above says you aren't done shocking until you have less than .5ppm CC, you are only losing 1ppm FC overnight, and water is clear.

    I have 0 CC's, the water is clear. But I'm losing what seems to be more than 1ppm FC during the night, and then a documented "butt load" of 3-4ppm FC during the day. So I cannot be done shocking correct? The little algae pockets are really showing improvement so I know I'm making progress but how much longer do I keep this up? I'm meeting 2 out of the 3 criteria for shocking, can I begin to reduce the FC down to maintenance, considering that I must begin overdosing during the night so that levels never drop below minimum during the day?
    18,000 Gallons plaster, in ground. Pentair quad cartridge filter system charged w/DE. Built in the early 70's. Location: Bakersfield California. Summer temps from early May to late September, up into the 100'sF. Very low shade over pool, not until LATE evening. Palm tree drops pods from neighbors yard.

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    Butterfly's Avatar
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    Re: Losing a lot of chlorine during the day

    It is great that you seem to have made much improvement, but you are not done shocking until you meet all three criteria.

    An FAS/DPD test is needed to perfom the OCLT.

    If you get the shock process close to complete, but not complete, whatever is brewing in the water will come back and bite you later.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Re: Losing a lot of chlorine during the day

    Quote Originally Posted by Jackslap
    Quote Originally Posted by frogabog
    With a CYA of 35 you should be dosing to 7ppm at night, which should leave you with 3-4ppm at the end of the day. It looks to me like you aren't quite hitting target. Loosing 50% of your chlorine every day is what's supposed to happen. To maintain minimum, you have to add enough every night so that loosing half the next day leaves you back at minimum.

    This just occured to me tonight while I was dosing the pool. Stupid me has not been taking into consideration that I should be overdosing during the night so that the levels never drop below the minimum during the day.

    Here's what happened the past 24 hours.

    Raised FC levels to 13 last night. It was all the bleach I had on hand even though the chlorine/CYA chart said I should be at 16. Pool sat overnight at that level. I was unable to check the levels this morning due to Sunday activities elsewhere, and only was able to check them at about 2:30 this afternoon. At that point the FC was 7. So I lost 6 ppm during over night and during the day. I have noticed that when taking the morning readings and comparing them to evening readings I am indeed losing about 3-4 ppm during the day, presumably from just sunlight.

    So......the pool shock page in pool school and one of the mod's sigs in the posts above says you aren't done shocking until you have less than .5ppm CC, you are only losing 1ppm FC overnight, and water is clear.

    I have 0 CC's, the water is clear. But I'm losing what seems to be more than 1ppm FC during the night, and then a documented "butt load" of 3-4ppm FC during the day. So I cannot be done shocking correct? The little algae pockets are really showing improvement so I know I'm making progress but how much longer do I keep this up? I'm meeting 2 out of the 3 criteria for shocking, can I begin to reduce the FC down to maintenance, considering that I must begin overdosing during the night so that levels never drop below minimum during the day?
    You must meet all 3 criteria like Butterfly stated!
    IMO, (because of the 100% sun your receiving) It's best to overshoot your shock level about 3ppm more than the CYA shock value.
    This will give you a slight advantage with never getting under your shock value #.
    Every time you fall below that shock value, your just letting the organic's fight back and they win some and slows your progress to a crawl! You can't be sleeping on the job when in the shock process.


    Chuck
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