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Thread: Can't keep chlorine in pool

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    Can't keep chlorine in pool

    I bought a home with a pool last year. We ended up draining it and starting over.
    We did pretty well once I got the numbers in proper range.
    My pool guy said it was one of the cleanest pools he closed last fall. So yea me and thanks for everyones help.

    This year I'm having trouble keeping the chlorine levels up and stable.
    Yesterday I put in 242oz. and tonight zero chorline.

    tonights numbers. 7/17

    FC 0
    PH 7.6
    TA 160
    CH 260
    CYA 40

    Im struggling to understand why since most numbers are well within range.

    I have to be missing something but no idea what.

    Water looks and feels great.

    thx
    jp
    30x18 Gunite inground pool with fiberglas side walls, 20k gallons, Sta Rite Sand filter .75hp pump

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    BoDarville's Avatar
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    Re: Can't keep chlorine in pool

    Odds are you have something organic (microbial) that is living in the pool. Most likely, it is an early stage of algae that is not yet visible -OR - you could have algae in a hidden area such as behind a light fixture or around a ladder. Both will consume chlorine.

    Can you run a CC (Combined Chloramines) test with your test kit? FC + CC = TC (Total Chlorine). If CC is greater than 0.5 ppm, this would confirm my hypothesis.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
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    Re: Can't keep chlorine in pool

    FC and CC also zero
    30x18 Gunite inground pool with fiberglas side walls, 20k gallons, Sta Rite Sand filter .75hp pump

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    Re: Can't keep chlorine in pool

    I just ran your numbers through the poolmath link at the top of the page, and you don't appear to be adding enough CL to shock the pool. Use the link to double check your numbers for shock. Check the details on how to perform a SLAM procedure in the Pool School Index. Make sure you have extra CL on hand, as you will need it to maintain the shock level in the pool throughout the day/night.

    Jim
    16x32 DiamondBrite kidney, 12,500 gal. (circa 1985) 3/4hp Hayward SII, Harmsco BF84, Taylor K-2006, Hayward SwimPure Plus / Tcell-15
    Boca Roton, Fl. USA.

    prior 17k gal. vinyl, Sand filter

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    Butterfly's Avatar
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    Re: Can't keep chlorine in pool

    jp, you need to do the SLAM process. Follow it to a T:
    http://www.troublefreepool.com/conte...tain-shockingl
    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. ~

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    Re: Can't keep chlorine in pool

    Are you using your own test kit? (You know I have to ask).

    It sounds like an Algae bloom trying to get started to me. SLAM time.
    TFP Moderator Chris V. ~16K Pool & Spa, 48NSF DE, IG Plaster Circa 2000, Intermatic PE653, Challenger pump with a 2 speed B2984, 20gal stenner chlorine injection, Houston, TX
    One cannot follow Islam and Christianity at the same time, nor can one follow pool store methods and TFP at the same time.
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    Re: Can't keep chlorine in pool

    Thanks for the response's. I have the tf-100 test kit.

    Will start slaming tonight. If im reading the chart right I should start adding 484 oz. of liquid bleach to go from zero to a fc of 16 ?
    30x18 Gunite inground pool with fiberglas side walls, 20k gallons, Sta Rite Sand filter .75hp pump

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    Re: Can't keep chlorine in pool

    Assuming you are using 8.25% bleach, that's what I came up with too. Good luck!
    Jim
    16x32 DiamondBrite kidney, 12,500 gal. (circa 1985) 3/4hp Hayward SII, Harmsco BF84, Taylor K-2006, Hayward SwimPure Plus / Tcell-15
    Boca Roton, Fl. USA.

    prior 17k gal. vinyl, Sand filter

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    Re: Can't keep chlorine in pool

    More bleach!
    13,500 gal, installed 2006, vinyl, 24' round, AG - sand filter, 1.5 hp pump, TF-100 test kit w/ SpeedStir
    Lower NC

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    Casey's Avatar
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    Re: Can't keep chlorine in pool

    Quote Originally Posted by jp5touring View Post
    Thanks for the response's. I have the tf-100 test kit.

    Will start slaming tonight. If im reading the chart right I should start adding 484 oz. of liquid bleach to go from zero to a fc of 16 ?
    Shock LevelAndMaintain!
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

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    Re: Can't keep chlorine in pool

    Every time I read your subject line I visualize little CL molecules climbing out of the side of the pool and running away screaming.

    TFP Moderator Chris V. ~16K Pool & Spa, 48NSF DE, IG Plaster Circa 2000, Intermatic PE653, Challenger pump with a 2 speed B2984, 20gal stenner chlorine injection, Houston, TX
    One cannot follow Islam and Christianity at the same time, nor can one follow pool store methods and TFP at the same time.
    Pool School -- Pool Math -- TF-Test Kit

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    Re: Can't keep chlorine in pool

    Quote Originally Posted by karmabiker View Post
    Every time I read your subject line I visualize little CL molecules climbing out of the side of the pool and running away screaming.

    HAH Never thought of it that way,,, To bad their all carrying nickels and dimes.

    Added 484 oz late last night and scrub the pool didnt have time to vacuum. I hade a 12 hr day at work.

    Did a quick check with the OTO test kit at 7am CL was so high it turned red instead of yellow.
    at 5:30 today was back to zero.

    I added another 484 oz. will have some dinner and scrub and vacuum tonight. Filter has been non stop.

    PH 7.5
    CL 0
    TA 150
    CYA 35

    also going out and stock up on bleach.

    Friday I will come home on lunch test and add CL.

    Will be close to home this weekend. will test a few times during the day.
    30x18 Gunite inground pool with fiberglas side walls, 20k gallons, Sta Rite Sand filter .75hp pump

  13. Back To Top    #13

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    Re: Can't keep chlorine in pool

    I think we have it under control. FC levels are starting to stabilize. Going to due my overnight FC test and see if it hold in the morning.

    Water looks good CC is zero for the past day or so. I pulled the pool ladder and the rubber pucks or covers had some mold/algae on them not a ton
    but covered. Some had a red tint..

    Is there a easy way to test the bottom pool drain ? Should it be stronger or weaker then the skimmer ? Just have a feeling it could be stronger.
    Their is flow at filter valve but just hard to tell.

    Thanks for the input everyone.
    30x18 Gunite inground pool with fiberglas side walls, 20k gallons, Sta Rite Sand filter .75hp pump

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    Re: Can't keep chlorine in pool

    Yeah!
    16x32 DiamondBrite kidney, 12,500 gal. (circa 1985) 3/4hp Hayward SII, Harmsco BF84, Taylor K-2006, Hayward SwimPure Plus / Tcell-15
    Boca Roton, Fl. USA.

    prior 17k gal. vinyl, Sand filter

  15. Back To Top    #15

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    Re: Can't keep chlorine in pool

    Dang Close Overnight test showed a drop of 2 maybe 3 ppm,, We have had a few heavy thunderstorms past two days doubt that helps.
    30x18 Gunite inground pool with fiberglas side walls, 20k gallons, Sta Rite Sand filter .75hp pump

  16. Back To Top    #16
    Butterfly's Avatar
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    Re: Can't keep chlorine in pool

    Keep SLAMing!

    Got a pic for us?
    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!

  17. Back To Top    #17

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    Re: Can't keep chlorine in pool

    I slamed another day and FC held overnight. How much is typical FC loss in a Sunny day ?

    It still drops more then I like. I also check it late in the day. 7,8pm I know i should take that into account.
    30x18 Gunite inground pool with fiberglas side walls, 20k gallons, Sta Rite Sand filter .75hp pump

  18. Back To Top    #18

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    Re: Can't keep chlorine in pool

    I think Im going to check behind my light just for grins, I did pull the ladder and scrub that well.
    30x18 Gunite inground pool with fiberglas side walls, 20k gallons, Sta Rite Sand filter .75hp pump

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    bridgman's Avatar
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    Re: Can't keep chlorine in pool

    Typical loss on a sunny day at "normal" FC levels (with appropriate CYA) seems to be 2-4 ppm, depending on whether it's sunny or SUNNY.

    Losses will be higher at SLAM levels since it's more a percentage than an absolute # of ppm, so you'll be losing a lot more during the SLAM than you would once the SLAM is completed and you go back to normal levels.
    Cedar hot tub, 680 US gallons - Snorkel wood-burning heater, canoe paddle, "offline" Intex 1000 GPH pump/filter with skimmer

  20. Back To Top    #20

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    Re: Can't keep chlorine in pool

    If you are at slam levels you will lose a bunch during the day. At target levels for your CYA if you target the high side of recommended it shouldn't drop below the low side. Generally 2-5 ppm.
    TFP Moderator Chris V. ~16K Pool & Spa, 48NSF DE, IG Plaster Circa 2000, Intermatic PE653, Challenger pump with a 2 speed B2984, 20gal stenner chlorine injection, Houston, TX
    One cannot follow Islam and Christianity at the same time, nor can one follow pool store methods and TFP at the same time.
    Pool School -- Pool Math -- TF-Test Kit

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