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Thread: HELP! Cannot pass OCLT despite raising FC targets

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    Exclamation HELP! Cannot pass OCLT despite raising FC targets

    Last year, with the help of this forum, I took control of my pool, and bought the Taylor K-2006 FAS/DPD test kit. I stopped going the the pool store and began using liquid chlorine (12.5%) as my sanitizer after having major issues with algae during pool opening. BBB method worked well for me, so I was looking forward to an easier opening this year. On June 4, pool opened with water green and FC 0, pH 7.8, TA 90, CH 170. I ran out of the CYA test, so could not determine exact amount of shock to add to SLAM. Blindly added a few jugs of liquid chlorine, and the pool cleared up within a few days. Brought water sample to Leslie's so I could have CYA tested until my new bottle arrived, and they told me it was 70 (which I thought was low considering it was at least 100 at closing, and we did not drain the pool). So I based my SLAM level on CYA 70, and SLAM target was FC 28. I followed the Pool Math instructions religiously, and water stayed crystal clear, but did not pass OCLT. Hubby convinced me things looked good, and we stopped running filter 24/7, but within 2 days, pool got cloudy again. Had to SLAM again, hubby added algaecide and after a few days, water became crystal clear, but still failing OCLT (anywhere from 4-10). Have been brushing every day, using Aquabot as well to get the the bottom of pool, constantly adding chlorine to maintain FC 28-30. Tried to test pH, but results turn purple due to high FC.

    By then, my own CYA test arrived, and I got a reading of 90, so I assumed I failed OCLT because I missed SLAM target. For the past few days, I have been raising my FC target but have been unable to pass the OCLT. Here are my FC readings:
    6/15 - during the day tested FC 35-38. Tested at sundown FC 27.5. Added 199 oz chlorine to raise FC 39.5
    6/16 - 7 am reading FC 35.5, added 1 gallon to raise FC to 43. 11 am FC 39.5, added 96 oz to raise FC 45. 3:45 pm FC down to 35. Added 2 more gallons to target FC 50. 8:30 pm FC 46. Added 48 oz to bring up to FC 49
    6/17 - 7 am FC 42.5.

    Water is still crystal clear. Hubby is suggesting we just let FC level go down so we can swim and enjoy it, especially for Father's day tomorrow. I am ready to give in because it is so beautiful out, and pool looks so inviting, and I am tired of adding all this chlorine with no results.

    Why am I still failing OCLT despite having such high FC levels that exceed the target for my CYA level? I have repeated the CYA test multiple times, but am pretty sure it is at 90.
    Are my FC levels now too high to swim in the pool?
    Please Help!
    15K Inground. Vinyl liner. Hayward sand filter. Aquabot Turbo T robotic cleaner.

  2. Back To Top    #2
    needsajet's Avatar
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    Re: HELP! Cannot pass OCLT despite raising FC targets

    You need to be a bit more sure of your CYA level. You could try a diluted CYA test by mixing up two cups pool water with two cups tap water in a clean container. Then take your testing sample from that water. Double the reading to get your CYA level, as a check against your high reading.

    Also, for the OCLT, re-test FC 30 to 45 minutes after the final evening chemical addition. This should occur after sunset, and is the beginning baseline for the OCLT. The endpoint of the OCLT is the FC level before sunrise.

    People sometimes wonder whether or not the pump should be running for an OCLT. If you are SLAMing, your pump should be running 24/7.

    It is generally considered impractical to run the pool at high CYA. Consider the advantages of lowering CYA to 50 PPM which might make everything a bit easier to accomplish. This would require a partial drain/refill and if you decide to do this, you need to consider the water table in your area and any risk of your pool lifting.
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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    Re: HELP! Cannot pass OCLT despite raising FC targets

    Welcome to TFP!

    My plan would be to stop the SLAM and enjoy the pool for Father's day weekend and start the SLAM ASAP after you are done swimming for the weekend. As long as there is the minimum amount of FC for the CYA level you should be safe to swim in the pool.

    The first step before starting the SLAM should be to replace 50% of the water which will make the SLAM process much easier and use far less chlorine to finish the SLAM. For NJ, a CYA level of 50 is about as high as I would go for a non SWG pool.

    Even though the water looks clear, the OCLT is telling you the truth, their are organics consuming the chlorine and you have to complete the SLAM process to get rid of all the organics. It might take a week or so and you just need to be patient with the process.
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    Re: HELP! Cannot pass OCLT despite raising FC targets

    Probably going to go against the grain here, but I agree with ping and needsajet as well

    You need to get as accurate a reading as you can on the CYA. Pool Store numbers aren't to be trusted. I know in PA, pretty close to you I go for 40 or 50 at the start of the season, we enjoy the season, attempt to properly close and the next year I have a CYA of 0 with no water exchange. That could have been a factor with you as I have read others experience the same type of offseason results. You will get a more accurate result with your test. Keep in mind of all the tests that ones subject to a pretty large window of interpretation, but do what you can with it and have a second set of eyes verify your result.
    Test on a sunny day, get your sample and allow it to come up in temp some.
    Perform the test with your back to the bright sun, view tube at waist level.
    Record result.

    Using that same water, empty view tube back into the little red-capped bottle, hand off sample to second set of eyes.
    Have them stand back to the bright sun, view tube at waist level, compare results.
    If it's ballpark consider it the result.
    If there is huge variance, try again. Don't reveal your number to the second set of eyes, to sway what they declare when they go through the exercise a second time.
    Once you establish a second CYA ~ get to target.

    If cya is high, I would bring to target or allow to fall to target and if your water is clear I would enjoy the pool this holiday weekend.
    I would then consider doing a water exchange to bring that CYA to a more manageable level, post holiday.

    If you are just going to live with the higher CYA I would realize that you are going to need to feed it more liquid chlorine to maintain target and if things get out of hand you will need even greater amounts to SLAM. Folks do manage with higher CYA levels, it just costs more to do so.

    But that pool is in your yard to enjoy, if your water is clear and you can keep it sanitized (that is determined by CYA levels and target FC) enjoy the pool this weekend and make decisions on higher CYA that you act upon once the hot weekend is over. Just please make sure you get as accurate a reading as you can with the CYA so you hit target for sanitation/health reasons and that you don't enter cloudy waters. If you go this route I would test a bit more frequently between now and final swim tomorrow just to make sure maintain target.
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    Exclamation Re: HELP! Cannot pass OCLT despite raising FC targets

    Thank you all for your quick responses and advice. I took Ping and DKT113's advice and did not add any additional chlorine yesterday so we could enjoy the pool this weekend. At 8 am was FC 31, and 4 pm FC 27, so the levels are going down pretty quickly. I plan to go one more day without adding more chlorine, and will drain/refill tomorrow night to lower CYA. As needsajet also suggested, I retested the CYA and had my husband test, and we were both certain it was at 90.

    I have 2 concerns:
    1) If the CYA is almost definitely at 90, why are there still organics in the pool if we have kept the water at shock level for so long? Where could the organics be hiding at this point? We did not put ladders in the pool yet, and have brushed manually daily, used the Aquabot to supplement, and even used a sponge to wipe down the entire 2 skimmers. Is it possible there are spores in the main drains at the bottom that we cannot reach and clean out?

    2) We plan to be away for a week starting 6/25. Family will be here and can add chlorine, but will probably not be able to continue to SLAM if process is not completed before we leave. We need pool to be clean and clear on Sunday 7/3 for a big party. Is it worth it to try to SLAM again after lowering the CYA, or would we be better off just trying to maintain the target FCs for the next 2 weeks, even if that means having to add more chlorine daily?

    Any more advice would be greatly appreciated!
    15K Inground. Vinyl liner. Hayward sand filter. Aquabot Turbo T robotic cleaner.

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    needsajet's Avatar
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    Re: HELP! Cannot pass OCLT despite raising FC targets

    Answers to first few questions: The SLAM is only a few days so far because it didn't really start until you had the correct shock level. Can't answer where algae might be hiding, just too many variables, but it sounds like you've tackled those possibilities well.

    If it were me, I would drain/refill and continue the SLAM now. Your water is clear, so you're not far off. Be sure you're doing the OCLT correctly (start the OCLT with the first test after your evening chlorine additions have mixed in well, sample in the morning before sunrise). The lower CYA will make it easier for your family to manage as well.
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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    Re: HELP! Cannot pass OCLT despite raising FC targets

    I finally passed the OCLT last night! All along during the SLAM, I was doing the OCLT incorrectly by not getting a sample closer to sunrise. When there was a drop in FC, I assumed it was organics in the pool, when it was probably the early indirect sunlight eating away the chlorine. The high FC levels probably didn't help either, skewing my test results because I needed so many drops, and probably needed more DPD powder. Huge lesson learned!

    My FC reading is now at 27, and I will let it fall to target levels and plan keep it there so I don't have to SLAM again. So relieved... Thanks again!
    15K Inground. Vinyl liner. Hayward sand filter. Aquabot Turbo T robotic cleaner.

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    Mod Squad tim5055's Avatar
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    Re: HELP! Cannot pass OCLT despite raising FC targets

    Quote Originally Posted by JeanF View Post
    I finally passed the OCLT last night! All along during the SLAM, I was doing the OCLT incorrectly by not getting a sample closer to sunrise. When there was a drop in FC, I assumed it was organics in the pool, when it was probably the early indirect sunlight eating away the chlorine. The high FC levels probably didn't help either, skewing my test results because I needed so many drops, and probably needed more DPD powder. Huge lesson learned!

    My FC reading is now at 27, and I will let it fall to target levels and plan keep it there so I don't have to SLAM again. So relieved... Thanks again!
    Great job!

    Now, stick around and help those following behind you. You may feel "new", but you have been through a SLAM and can provide valuable lessons and support to others.
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    needsajet's Avatar
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    Re: HELP! Cannot pass OCLT despite raising FC targets

    Great to hear Have fun with your pool !!
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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