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Thread: I have algae again!

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    Glock's Avatar
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    I have algae again!

    What causes algae growth? I got sick awhile back and let my FC drop to 0 for a few days and got algae. I followed the steps, passed the OCLT and have kept my FC at atleast 5 since then. Today, I have algae again! The water is crystal clear and has been for a few weeks. I will get a set of numbers in about 20 minutes.

    It has gotten cooler here and we have had quite a few cloudy days but I am running my pump 8 hours a day and keeping my FC up. Should I be shocking from time to time even if my FC is good and nobody has been in the pool?
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    Re: I have algae again!

    Not enought chlorine. We'll give a better answer when we see the full set of numbers, but the very short answer is "Algae grew in your pool because you didn't maintain a high enough FC level."

    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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    Re: I have algae again!

    Ok. I am about to go to lunch and get numbers but pool calculator says 3-7 ppm which is what I have maintained. I even test every day.
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    Re: I have algae again!

    Latest readings. This is what I have been at since the algae a month ago.

    FC 4.5
    CC 0
    pH 7.8
    TA 130
    CYA 50
    CH 140
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    Re: I have algae again!

    Shock your pool again, then keep the FC higher than you have been....maybe by 30-50% higher.

    I cannot explain why you have algae but I know for certain it grows when the chlorine is inadequate.
    Dave S.
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    Glock's Avatar
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    Re: I have algae again!

    Ok. I am going to vacuum it today even thought its cold. Probably freeze my baguettes off but it will be worth it. I will report back after the vacuum. I sure wish I could get my Ranger to work.
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    Re: I have algae again!

    With CYA at 50, an FC of 4 should be an absolute minimim, meaning that letting it drop to 4 every once in awhile will be ok. My CYA is also at 50, and my personal minimum is 6.

    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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    Re: I have algae again!

    That must be what it is then. I will keep my FC at 10 from now on. I hate having to brush this thing, especially since its cold. lol
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    Re: I have algae again!

    It's most likely poor circulation, especially bottom circulation which is notoriously poor in many circular above-ground pools (especially Intex) though yours isn't circular. You might try pointing your return somewhat downward to improve circulation to the bottom of the pool. How many returns do you have in the pool?
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: I have algae again!

    One return and the jet even though being pointed down is still pretty straight. The Doughboy return jet leaves alot to be desired. I am really considering replacing it and the skimmer with Hayward hardware.
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    Re: I have algae again!

    My pool (In Ground) is running an FC level of 7-12 typically no lower than 8 really - with a CYA of 55 or so. I have it higher due to the level of leaf debris that builds up between my visits to clean it out.
    Inlaws Pool Boy since June 14th 2012, Pool built ~ 2003, In-Ground, 16'x32'
    13500 gal, Vinyl Liner, Fiberglass Slide, TF-100 Test Kit, Hayward 210T
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    Re: I have algae again!

    Every calculator I have used has always said 3-7 ppm. That'll teach me! lol 10 is the magic number now. If I had known I was that close to the edge of algae I would have kept it higher. But, hey! We live and learn; right?
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    Re: I have algae again!

    Quote Originally Posted by Glock
    Every calculator I have used has always said 3-7 ppm. That'll teach me! lol 10 is the magic number now. If I had known I was that close to the edge of algae I would have kept it higher. But, hey! We live and learn; right?
    Just remember that 10 or greater FC means no pH measurements. I'd target 10 as the goal for the start of the day and let it drop down to 7? And then you will be able to measure pH at the end of the day.
    Inlaws Pool Boy since June 14th 2012, Pool built ~ 2003, In-Ground, 16'x32'
    13500 gal, Vinyl Liner, Fiberglass Slide, TF-100 Test Kit, Hayward 210T
    sand filter, A.O. Smith 1.5HP main pump motor (C48L2N134C1),
    Hayward SuperPump (model ?), Polaris 380 & PB4 Booster Pump

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    Re: I have algae again!

    You read my mind. I test FC in the mornings and all levels on Thursday evenings.
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    Re: I have algae again!

    Quote Originally Posted by Glock
    One return and the jet even though being pointed down is still pretty straight. The Doughboy return jet leaves alot to be desired. I am really considering replacing it and the skimmer with Hayward hardware.
    You have one return for an 18'x34' 23,000 gallon pool? No wonder you've got issues. There's no way you're going to get good circulation in such circumstances so anything getting dumped into the pool and settling where there is poor circulation can use up chlorine and any algae can then get started growing making the situation worse. By having a higher FC level where you easily measure it, you are just hoping that the FC in the poor circulation areas gets proportionally higher as well, putting it above the minimum level to inhibit algae growth.

    The Pool Calculator and the Chlorine / CYA Chart both assume reasonable circulation. My 16'x32' in-ground pool has 3 returns, 1 skimmer, and 2 floor drains.
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    Re: I have algae again!

    Can I run a 2nd return off a single pump? I guess I could. Shouldn't present a problem since its on the output side. I know that one return I have if you aim it up towards the top of the surface it moves water well past the halfway mark of the pool and not just a little. I can hold a pool noodle up to it and take it out of the water and it goes over half way across the pool. It has some serious pressure. Of course, hard plumbing is during the fall and the pipes will be 2" rather than 1.5" like they are now and that will lower the pressure some I imagine.
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    Re: I have algae again!

    I just added 605oz of 8.25% bleach to bring me 21 ppm and brushed the pool. the green cloud has already turned white but I will keep it at shock until it passes all the tests.

    1. CC is less than 0.5 ppm = 0 ppm
    2. An OCLT shows a loss of 1.0 ppm or less = Not yet tested
    3. The water is crystal clear = Cloudy
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    Re: I have algae again!

    Quote Originally Posted by Glock
    Of course, hard plumbing is during the fall and the pipes will be 2" rather than 1.5" like they are now and that will lower the pressure some I imagine.
    Actually, using larger piping will increase the water flow rate because there will be less loss in the piping. This assumes you keep the same return outlet (eyeball) size. You would only lower the flow rate in the pool if you increased the eyeball size.

    You should be able to add another return and still have substantial water flow, but be able to direct the second return to move water in the area where algae now seems to develop. Having two returns would have a lower flow rate from each, but total flow rate would be higher and circulation would be vastly improved.
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    Re: I have algae again!

    Then I will plan on adding a second while its down for the winter. I am going to buy the Hayward parts soon. I hate the doughboy inlet. Its rubberized and impossible to move unless the retainer ring is off completely. Looks like I will have a busy off season.
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    Re: I have algae again!

    Passed my OCLT last night. Crystal clear and 0 CC too. Finally. Now to keep a better eye on the FC. Goign to strive for 10ppm in hopes I never get below 5.
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