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Thread: Chlorine levels dropping

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    Chlorine levels dropping

    This morning's numbers (from a TF100):
    pH: 7.4-ish
    FC: 1.5
    CYA: 50-60
    TA: 80-90

    When I opened the pool three weeks ago, it was the first time in two years (new owner of the house). The pool cover was very old and had plenty of holes, so there was a LOT of gunk in the pool. I've gotten the water cleared up, and am down to just a bit of dirt that settles on the bottom every day. I'm still running my pump 24/7.

    My FC is still dropping every day. I'm having to add a gallon or so of bleach a day. I'm thinking I need to just slowly keep upping my CYA with stabilizer to the 70-80 range.

    Questions:
    1) Is that the right strategy?
    2) Since I'm running my pump 24/7, does it really take a week to get the full adjustment from adding stabilizer?
    3) Over the last week, I've noticed an increasing amount of bubbles in the return. Is this a concern?
    4) How do I know when it's okay to drop my filtering to just a few hours a day?
    Thanks,

    Kansas City, MO area
    13,500 gal AG vinyl
    55GPM Waterway sand
    1HP MaxFlow pump
    Intex SWCG

  2. Back To Top    #2
    JasonLion's Avatar
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    Re: Chlorine levels dropping

    You should do an overnight FC loss test to see if there is something organic in the water using up chlorine.

    CYA can take up to a week to dissolve. Often it dissolves more quickly than that, but you can't count on it.

    Bubbles in the return are either an SWG or a suction side air leak. Check the seal on the pump strainer basket lid and make sure there isn't a vortex in the skimmer drawing in air.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Butterfly's Avatar
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    Re: Chlorine levels dropping

    Welcome

    Stop adding CYA until you get your pool cleared.

    Your FC is too low for your CYA level. See the CYA/Chlorine chart in Pool School.

    What is the CC test result?

    How does the water look?
    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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    duraleigh's Avatar
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    Re: Chlorine levels dropping

    , and am down to just a bit of dirt that settles on the bottom every day
    I would suspect that to be dead algae. AS BF and Jason indicated, get your FC level up....quickly. Then, keep it up there until you can pass the overnight FC loss test.

    Do not increase your CYA.....you have enough.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  5. Back To Top    #5

    Re: Chlorine levels dropping

    I should have stated my CC is at .5 consistently. Sorry for forgetting that. I've not re-checked FC overnight, but it was stable for three days before I adjusted TA and CYA. I've just been adding bleach every morning to get it back up to 6.

    I'll check it again tonight and compare it tomorrow.
    Thanks,

    Kansas City, MO area
    13,500 gal AG vinyl
    55GPM Waterway sand
    1HP MaxFlow pump
    Intex SWCG

  6. Back To Top    #6

    Re: Chlorine levels dropping

    Okay, just checked twice and got two results. FC/CC for test 1 was 1.5/.5?, test two was 2/1. So, should I go to shock mode tonight, or wait and check in the morning to see if I lost chlorine overnight? If I wait, do I bring chlorine up to 6 (target according to CYA chart) tonight? If so, do I wait a half-hour and check it again?
    Thanks,

    Kansas City, MO area
    13,500 gal AG vinyl
    55GPM Waterway sand
    1HP MaxFlow pump
    Intex SWCG

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    frogabog's Avatar
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    Re: Chlorine levels dropping

    They would have told you to shock.

    Both test results tell you to shock, anything over .5ppm CC means shock.

    Maintain shock level. Shock till the overnight test is 0. Then you do "target".

    I'd also shock at the highest CYA level you think it could possibly be and add some error (overdoing CYA is easy). Missing shock level slows everything down. Test CYA again in a couple days to be sure.
    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.

  8. Back To Top    #8

    Re: Chlorine levels dropping

    I'm really confused. I've kept FC at shock level (16+) for three days. The overnight drop is minimal (1-2ppm), but I can't seem to get CC to drop below 0.5. The water is crystal clear. ph is holding steady at 7.5. CYA is 50.

    Do I need to keep shocking at this point? It would seem that since I started this second round of shock with clear water, it shouldn't be such a hassle to get CC to drop to 0.

    Am I missing something?
    Thanks,

    Kansas City, MO area
    13,500 gal AG vinyl
    55GPM Waterway sand
    1HP MaxFlow pump
    Intex SWCG

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    Mod Squad Bama Rambler's Avatar
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    Re: Chlorine levels dropping

    If you're losing 1-2 ppm overnight then yes, you should keep shocking. Once you kill whatever is causing the overnight loss your CC will probably go down.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Butterfly's Avatar
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    Re: Chlorine levels dropping

    Yes, keep shocking.

    I agree w/frogabog about shooting for the highest CYA shock level.
    With CYA of 60, shock level is about 24.

    Retest CYA again in a couple days.

    You are done shocking when you meet three criteria: See Red line in my sig.
    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!

  11. Back To Top    #11

    Re: Chlorine levels dropping

    and, sorry if this is a stupid question, but I'm working on the assumption that the kids should NOT swim while shocking.

    Correct?
    Thanks,

    Kansas City, MO area
    13,500 gal AG vinyl
    55GPM Waterway sand
    1HP MaxFlow pump
    Intex SWCG

  12. Back To Top    #12

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    Re: Chlorine levels dropping

    Correct.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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