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Thread: Can't kill this algae

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    Can't kill this algae

    I have been at this for weeks, so I figure it's time to get you involved. Let me just give you the latest by started with test results.

    12,000 gal above ground pool with a SWG

    FC - 16 ppm
    CC - 0
    PH - 7.6................but I just put a little shot of muriatic acid in so that should could down a bit.
    TA - 150
    CYA - 37

    Ok, I shocked the pool for more than a week by keeping it at 16 ppm on FC and through checking the pool twice a day. It turned from green to blue, but was still so cloudy that you couldn't see more than 2 ft deep. At this point just before sunset I checked the Chlorine levels while the SWG still had an hour or so left on the meter. The next morning it had only lost .5 ppm, so I thought that I was done. I backed off of the chlorine and over the process of 2 days and with a drop to 9ppm FC, the pool turned green again. So, I immediately started hitting it with bleach again and have been at 16ppm for 2 days with absolutely zero effect. I have been checking and adjusting every hour for 2 days now to make sure that there is no dip in FC, but there is no visible affect. Thinking to use algaecide, but everything on here seems negative against it. I went through 3 gallons of bleach yesterday keeping it at 16ppm and overall Ive had the chlorine levels high for weeks. Im not sure how to proceed to maximize my investment and advance the cause of a clear pool. Thanks in advance.
    Index AG 22'x52", 11,400 gallons, 1500 g/h pump with cartridge filter and SWG. Pool opened May 2014.

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    jeffchap's Avatar
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    Re: Can't kill this algae

    How did you obtain that CYA reading of 37 ppm? All of our testing rounds up to the next multiple of 10. 37 looks like a pool store testing value. For some reason, CYA is the test that they most frequently get wrong, often dramatically so.

    If that's the case here, your actual CYA level may in fact be much higher, and consequently your shock level may be higher than 16 ppm.

    If you do not have your own CYA test, you should get one ASAP and let us know what value you measure. Both the TF-100 and K-2006 test kits commonly recommended here contain a CYA test, as well as the FAS-DPD chlorine test you will need to perform a SLAM if that ends up being required in your case.

    In a pinch, Wal Mart sells an HTH 6-way test kit that includes a CYA test that you can use while waiting for your *real* test kit to arrive.

    Once we know your accurate CYA level we can proceed from there. But without that, we'd simply be shooting in the dark.
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    Re: Can't kill this algae

    on top of that you losing FC at that rate and having CC at 0 doesn't make sense. You need to get reliable test results first- buy one of those kits as already recommended and keep feeding it bleach based on your best guess until the kit arrives. Then you prob won't need anyone's advice .
    44k plaster pool, Pentair 011018 pump, DE6020 filter, LED lights, K2006 test kit

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    Re: Can't kill this algae

    This is a taylor test kit as recommended from this site. I said 37 because it was in between the 30 and 40 marks, closer to the 40....and I tested it twice.

    This test calculates CC by adding 5 drops of solution back to the test tube that was just turned clear by testing for FC. After adding 5 drops, it remained clear, as opposed to turning red or pink again....thus I marked 0. If I did the test wrong, please let me know.

    FYI....it's 97 and sunny here.
    Index AG 22'x52", 11,400 gallons, 1500 g/h pump with cartridge filter and SWG. Pool opened May 2014.

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    Re: Can't kill this algae

    Best practice is to turn off the SWG completely, have the pump and filter running 24/7. That way you know exactly how much you are losing. You said yourself the SWG ran for an hour after your test, then the next morning you'd only lost .5 ppm, and you backed off. That's guessing, and that's is what will extend your SLAM.
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    Re: Can't kill this algae

    Quote Originally Posted by Bensonspool View Post
    I have been at this for weeks, so I figure it's time to get you involved. Let me just give you the latest by started with test results.

    12,000 gal above ground pool with a SWG

    FC - 16 ppm
    CC - 0
    PH - 7.6................but I just put a little shot of muriatic acid in so that should could down a bit.
    TA - 150
    CYA - 37

    Ok, I shocked the pool for more than a week by keeping it at 16 ppm on FC and through checking the pool twice a day. It turned from green to blue, but was still so cloudy that you couldn't see more than 2 ft deep. At this point just before sunset I checked the Chlorine levels while the SWG still had an hour or so left on the meter. The next morning it had only lost .5 ppm, so I thought that I was done. I backed off of the chlorine and over the process of 2 days and with a drop to 9ppm FC, the pool turned green again. So, I immediately started hitting it with bleach again and have been at 16ppm for 2 days with absolutely zero effect. I have been checking and adjusting every hour for 2 days now to make sure that there is no dip in FC, but there is no visible affect. Thinking to use algaecide, but everything on here seems negative against it. I went through 3 gallons of bleach yesterday keeping it at 16ppm and overall Ive had the chlorine levels high for weeks. Im not sure how to proceed to maximize my investment and advance the cause of a clear pool. Thanks in advance.
    You can't take your starting OCLT reading while still adding chlorine to the pool.

    From the OCLT procedure:

    1. If you have an SWG, tablet chlorinator, or other chlorine feeder, shut it off completely.
    2. After the sun goes down, and at least 30 minutes after your last chemical addition of the day, test your water for FC using the FAS-DPD test making sure your FC level is at least above 3ppm.

    Pool School - Perform the Overnight FC Loss Test (OCLT)

    You failed to follow procedures, and let your FC down to soon, this is why your pool is again green.

    Algaecide does not kill algae, chlorine does.

    Also, your pH test is going to read falsely high when FC is above 10ppm, and is one of the reasons it is lowered to 7.2 before the SLAM.

    Double check your CYA and continue the SLAM. Be sure to brush as often as you can.

    Dom
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    Re: Can't kill this algae

    yes, I am brushing regularly. On the SWG remaining on......after fighting it for so long, I just figured a .5 loss had to mean we were in business, especially since the SWG is set up to disperse chlorine over several hours and the pool sat for several hours without it being on. Just very surprised that the algae is that aggressive and that hard to kill. Also surprised that leaving the unit on for an extra hour would create that much difference in the numbers. Also surprised that after working with it so long the problem wasn't resolved. It seems people typically have it cleared in a week. Thanks for the help. Ill keep you posted.
    Index AG 22'x52", 11,400 gallons, 1500 g/h pump with cartridge filter and SWG. Pool opened May 2014.

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    Re: Can't kill this algae

    I was experiencing higher than normal FC usage, although CC was always .5 or less. My SWG was running nearly full time, and I was still adding bleach to keep up. Following heavy use over Fourth of July weekend, it turned green.

    I SLAMMED for a couple of days and once it was done, my FC burnoff has returned to normal. I've been able to cut my SWG run time way back again.

    I must have had a nascent algae breakout that was just barely being kept down. The SLAM appears to have eradicated it completely. I took my FC all the way to 36 ppm initially (CYA=80). You might try bumping yours a little higher than 16, maybe 20-24, for a couple of days to see if that helps any.
    25000 gallon free-form gunite
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    Re: Can't kill this algae

    I did decide to bump my chlorine level up a little bit and the pool does seem to be making greater progress. I am seeing deeper and it's blue again. Definitely making the right kind of progress. It's amazing that a slightly premature stop to my slam set me back another 2 weeks!

    on another note...I think that could have used a super chlorinated start to my pool season. I followed the pool closing instructions last year, but still ended up with algae growth as soon as the water thawed and the sun started warming things up post winter. One way or the other, it's been a fight since. But I don't top my pool off with municipal water. I have well water.

    Last year everything was perfect all season.....this year has been tuff!
    Index AG 22'x52", 11,400 gallons, 1500 g/h pump with cartridge filter and SWG. Pool opened May 2014.

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    Re: Can't kill this algae

    Bacteria and algae colonies double in size every 1 to 4 hours depending on type. Once they get going it is much harder to stop. As they get larger they build a biofilm around them to protect themselves from chlorine. There are millions of cells reproducing before the water even begins to cloud, remember they are microscopic. By the time the water starts to turn cloudy you already have a LOT of bacteria/algae in the pool. By the time it is green there bazillions and jillions in there.
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    Re: Can't kill this algae

    Not sure if anyone suggested super cleaning your ladder. AG pool ladders are notorious for hiding algae underneath. Might be worth pulling them out, inspecting and giving a good scrubbing.
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