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Thread: Unable to pass OCLT

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    Unable to pass OCLT

    Hello everyone - I've been having issues with passing the OCLT. This is my 4th night failing despite following it almost exactly. I've added over 20 gallons of
    10% sodium hypochlorite and my results haven't even really been improving, but the pool itself looks crystal clear. I washed out the cartridge filters completely, and I took apart and cleaned the lights and the drains in the spa that I saw some algae growth behind. I've been brushing and vacuuming every day. But every night I've been losing about 4-5ppm of free chlorine. For example, I tested it this night and had 20ppm chlorine at 8:00pm, and only 15 at 12:05am. What else am I doing wrong? Could it be from the leaves and other junk being blown into the pool due to crazy winds lately?

    17,000 gallon pool
    CYA: 30
    pH: 7.4 (from before bringing the chlorine high)
    CH: 370
    TA: 100

    Thanks!

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    Patrick_B's Avatar
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    Re: Unable to pass OCLT

    Welcome to TFP!

    What is your CC number?
    How long have you been clear, and what was the cause for the SLAM? Did you have a bad Algae bloom?
    TFP Moderator
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    BayScoutTim's Avatar
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    Re: Unable to pass OCLT

    Hi Xdxsc. . . . Welcome to TFP!

    Are you using one of the approved test kits to get your results? You need to add your pool equipment in your signature so the experts can help you solve your issues. Your location-region, state, etc. helps as well.

    Check your ladder or remove it from the pool if you can. Remove any "floating things" from your pool, these areas are a breaking ground for algae.

    With that said, be patient. You may need to raise your CYA to get the results you want. One more thing . . . . Did you SLAM your pool? All this information is in the pool school.
    BayScoutTim
    ---------------------------------------------------
    :: 28' round Doughboy AG (18,400 gallons) :: Hayward 1-1/2 hp Power-Flo Matrix pump :: Hayward Pro Series 21" top mount high-rate sand filter 65GPM :: Hayward Vari-Flo XL 7-way valve :: AquaBot Breeze 4WD :: TF-100 XL test kit :: SpeedStir magnetic stirrer ::

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    Re: Unable to pass OCLT

    When you perform the OCLT, you do so to determine if there are organics in your water....demonstrated by the overnight loss of FC in excess of 1 ppm. That's what's happening in your pool.....you still have organics in the water.

    Keep your FC at SLAM value. When the organics have all been removed, you will pass.

    You are not doing anything wrong....just stay the course.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Unable to pass OCLT

    in only 4 hours of no sun. (8PM to 12 AM) 5ppm loss is a lot.


    What was the condition of the pool before starting the slam?

    Its hard to tell from your original post how many days you've been SLAMing your pool. It says you failed the OCLT test 4 times. Have you been shocking for many days before trying the OCLT tests or have you been SLAMing for only 4 days?

    If you've only been SLAMing for 4 days that's a bit on the short side to be able to completely kill algae and remove it. Given your 5PPM loss in 4 hours without sun, leads me to believe your just not finished with the SLAM process. Also given that you've seen algae behind lights and jets, there could be more your not seeing that is playing a roll in this.

    I would say give it 2 more days of SLAMMING, check lights, filters, ladders, and anything else and then give us an update.
    12500 gallons, 24 foot round above ground
    Hayward Sand filter, Pentair OptiFlo 1HP 2-Speed pump

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    Re: Unable to pass OCLT

    To the experts: Is there a minimum amount of time for what TFP considers a proper OCLT test?

    I have no facts or proof, but I would suspect most OCLT tests are closer to 8 hours from test to test. I've never seen it mentioned but is 4 hours enough to get a reading for Over night chlorine loss?
    12500 gallons, 24 foot round above ground
    Hayward Sand filter, Pentair OptiFlo 1HP 2-Speed pump

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    Re: Unable to pass OCLT

    I have seen this take 2 weeks or more for pools with hidden problems.
    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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    Mod Squad Bama Rambler's Avatar
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    Re: Unable to pass OCLT

    Quote Originally Posted by scott.MI
    To the experts: Is there a minimum amount of time for what TFP considers a proper OCLT test?

    I have no facts or proof, but I would suspect most OCLT tests are closer to 8 hours from test to test. I've never seen it mentioned but is 4 hours enough to get a reading for Over night chlorine loss?
    4 hours should be plenty long enough to lose 1 ppm FC by organics. I probably wouldn't go less than 4 and certainly a little more would be better, but 4 hours should constitute a valid test.
    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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    Re: Unable to pass OCLT

    The OP mentioned leaves and other junk being blown into the pool. These certainly contribute to the chlorine loss. He needs to eliminate this before attempting the OCLT.
    7,500 gal, IG pool, L shape 22' x 15', 1.5 hp pump, cartridge filter, AquaPlus SWG/Controller, Pebble-Tec liner.

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    Re: Unable to pass OCLT

    Thanks for all the replies!

    My CC level has been running 0 to 0.5.
    I started SLAMing because I kept losing lots of chlorine overnight to the point where I was running at 0 FC for a few days. I've purchased and been using the TF-100 kit that you guys reccomend.
    The condition of the pool itself has never been below slightly cloudy.

    I actually miscounted, today is going to be day #7 of SLAMing.

    With regards to the stuff floating in the pool, I've been trying my best to keep it clear of debris but its difficult due to windy weather blowing pines and such into the pool.

    I do notice a thin black layer on the bottom of the pool that seems to come back despite brushing and vacuuming it away every day. It usually returns by that same night. Could that be black algae?

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    Re: Unable to pass OCLT

    Could that be black algae?
    No. It is most likely dead algae and possibly just some dirt mixed in. Vacuum it daily and you should begin to see a reduction.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Butterfly's Avatar
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    Re: Unable to pass OCLT

    You need to add your pool equipment in your signature so the experts can help you solve your issues. Your location-region, state, etc. helps as well.
    Go to User Control Panel (upper left) select Profile, then Edit Signature


    Check your ladder or remove it from the pool if you can. Remove any "floating things" from your pool, these areas are a breaking ground for algae.
    If you have any lights, (turn off power/breaker) remove light from niche and brush/clean it out. Expose it to the SLAM process.
    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: Unable to pass OCLT

    Anything new to report? Would be interested to know if you've solved the problem and passed your OCLT yet
    12500 gallons, 24 foot round above ground
    Hayward Sand filter, Pentair OptiFlo 1HP 2-Speed pump

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