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Thread: Algae despite chlorine level of 1.5

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    Algae despite chlorine level of 1.5

    Hi all, I've been here a while off and on and I've been using store bought bleach to keep my FC levels around 1-1.5 for a couple months now. I did my initial tests with my TF-100 kit and several follow up tests since then. But I've not tested anything but chlorine levels for about a month. SO......I notice this algae starting to develop in the small pits inside my plaster, it's getting harder and harder to keep away. I decide to check things and it turns out my PH is high. Around 8, maybe even like 8.1. Chlorine levels have been steady and I've even raised my FC levels to around 8 once in the last month just for the kicks while the family was out of town. I don't understand how the algae could be forming if my chlorine is in check. Is it the PH that is causing my problems?

    My Total Alkalinity is 100-110 level according to TF-100. It is within range and does not need to be adjusted according to the instructions. But the PH is getting high and must be lowered. If I lower it, can I expect this algae problem to go away? Of course all the people that I talk to IRL are recommending algaecide etc. But I know better. I know you guys can help me. What else do you need to know from me to solve this?

    Also, how long will it take to solve? I have a bunch of people coming over 3 evenings from now. It would be nice to have this cleared up by then, but that is wishful thinking I'm sure. I'd scrub most of it out and make sure my chem levels were safe before then of course.

    BTW I've never added any Borax to the pool. I'm reading about Borates in pool school right now and wondering if I should be using it. Yes?
    18,000 Gallons plaster, in ground. Pentair quad cartridge filter system charged w/DE. Built in the early 70's. Location: Bakersfield California. Summer temps from early May to late September, up into the 100'sF. Very low shade over pool, not until LATE evening. Palm tree drops pods from neighbors yard.

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    Richard320's Avatar
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    Re: Algae despite chlorine level of 1.5

    pH is too high, but that doesn't cause algae. It needs to get fixed.

    Your FC is low, even for a pool with no CYA in the water. And I'll bet you have CYA (aka stabilizer or conditioner) in your water.

    Your condition is probably the most common thing we see that drives people to the internet for pool answers - High CYA. If you've been feeding it with pucks in a floater, or using powdered "shock", it's almost a certainty. I'd bet heavily on that one, with odds!

    You really need to post a full set of test results. A full set of results will tell us and you if you need to do a partial drain or not. No point adjusting pH if you end up pumping half of it out.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    dmanb2b's Avatar
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    Re: Algae despite chlorine level of 1.5

    Welcome back Jack...last I recall we had you raise CYA to at least 30. FC should be at 3-4ppm, not 1-1.5...that's why the algae is sprouting
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

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    Re: Algae despite chlorine level of 1.5

    Thanks Dman, CYA was indeed elevated. Ended up going to 40 according to my test results chart. So.....my FC levels stay around 1.5 or so. You are suggesting 3-4, but I'm confused. Isn't that unsafe for swimming?
    18,000 Gallons plaster, in ground. Pentair quad cartridge filter system charged w/DE. Built in the early 70's. Location: Bakersfield California. Summer temps from early May to late September, up into the 100'sF. Very low shade over pool, not until LATE evening. Palm tree drops pods from neighbors yard.

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    Richard320's Avatar
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    Re: Algae despite chlorine level of 1.5

    No. Your tap water is probably 1 ppm, maybe even more, and you drink that!

    The CYA buffers it; it's a chemistry term that I learned in college chemitry a long time ago, so I'm not able to explain it. But 4 ppm with CYA 40 is safer to swim in than 1.5; your level is too low to kill algae, let alone bacteria or viruses!
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Algae despite chlorine level of 1.5

    Wow, so where in the heck did I read that FC levels should remain between 1 and 2? Am I going mad? I swear that is what I read a while back on a test kit that my dad was using for his pool. So at what FC level does it become unsafe?
    18,000 Gallons plaster, in ground. Pentair quad cartridge filter system charged w/DE. Built in the early 70's. Location: Bakersfield California. Summer temps from early May to late September, up into the 100'sF. Very low shade over pool, not until LATE evening. Palm tree drops pods from neighbors yard.

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    JasonLion's Avatar
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    Re: Algae despite chlorine level of 1.5

    The appropriate range for FC depends on the CYA level. See the Chlorine / CYA Chart in Pool School.
    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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    dmanb2b's Avatar
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    Re: Algae despite chlorine level of 1.5

    As Jason mentioned, you should refer to the FC/CYA chart he linked. Many consider anything below shock level as acceptable for swimming.
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

    Pool School, TFTestKits, Pool Calculator

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