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Thread: persistent low grade algae?

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    persistent low grade algae?

    Had a little bit of algae in the pool, CC=0.5. shocked to CL=18 with CYA=50, overnight CL loss was 0.5 with the very first testing. So I let the CL drift down. On next testing, CC is still 0.5 with normal within range CL level. Brought CL back to 18, brushed pool better this time. let CL drift down to normal range again. test: CC 0.5 again. Is there still algae in the pool? What am I missing? Water is sparkling clear.
    Irregularly shaped IG pool with aggregates of squares and rectangles, spa overflows to pool
    21K gallon, Pebble tec, 450 sq ft, 125 GPM cartridge filter, 1hp pump, 1.5hp booster pump, Jandy heater,
    2 skimmers, 2 main drains, Hayward Navigator automatic vacuum connected to one of the skimmers

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    Re: persistent low grade algae?

    Is there still algae in the pool?
    Why do you think that....because of the .5 CC's?

    The three criteria are....

    1. Your water is crystal clear.
    2. You lose less than 1.0 FC during the FC overnight loss test
    3. Your CC's test is .5 or less

    You're done.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: persistent low grade algae?

    Thanks! My CC has always been zero! The pink tinge confuses me.
    Irregularly shaped IG pool with aggregates of squares and rectangles, spa overflows to pool
    21K gallon, Pebble tec, 450 sq ft, 125 GPM cartridge filter, 1hp pump, 1.5hp booster pump, Jandy heater,
    2 skimmers, 2 main drains, Hayward Navigator automatic vacuum connected to one of the skimmers

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    Re: persistent low grade algae?

    Oh one more thing, CC was 0.5 even when there was visible algae. That's why I wasn't sure.
    Irregularly shaped IG pool with aggregates of squares and rectangles, spa overflows to pool
    21K gallon, Pebble tec, 450 sq ft, 125 GPM cartridge filter, 1hp pump, 1.5hp booster pump, Jandy heater,
    2 skimmers, 2 main drains, Hayward Navigator automatic vacuum connected to one of the skimmers

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    Butterfly's Avatar
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    Re: persistent low grade algae?

    If the .5 CC bothers you, you can shock it again if you want.
    But, probably sunshine will burn it off soon, as long as FC is maintained properly
    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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    Richard320's Avatar
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    Re: persistent low grade algae?

    Are you using the FAS-DPD test to measure your CC? If so, try using the 25 ml sample, then it will read by .2

    I'm too tired to figure out the exact mathematical examples, but I know that if FC was 4.2, and cc was .2, you'd measure 4.5 and 0 using a 10 ml sample. If you were at 4.1 and .2, you might end up reading 4.0 and .5

    Maybe you have something lurking behind the light, or in the filter, or even on pool toys or brushes. You could always toss all that stuff in and shock again.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: persistent low grade algae?

    I don't get it! Am I supposed to live with 0.5 of CC? I proceeded shocking again today b/c my FC loss per day is more than last June, even with lower water temp.

    numbers before shock at 11am:
    FC 5.0
    CC 0.5
    pH 7.5
    TA 70
    CH 420
    CYA 50
    temp 74
    pump running 5hr
    overcast today

    then, added MA to bring down pH to 7.2, brushed pool, added FC to shock level of 16.

    2pm: FC 15.0, added 26oz 10% FC to reach target of 16.0.

    3:10pm: FC 15.0, CC 0.5. added 26oz more FC to reach 16.0

    ok, with CC=0.5, my overnight FC was never more than 1.0 even before the very first shock (third try today), and water is clear. you may say that i didn't need to shock or I can stop. however, there were clouds of algae whenever I brushed the walls and getting worse. So visual observation did not match the numbers. After the first shock, green cloud is gone.

    With CC only = 0.5, I just dumped in enough FC to get to shock level the first time and let it drift down. I brushed the pool twice, but not everyday.

    5 days later, did a second shock after realizing CC is still 0.5, brushed everyday for 2 or 3 days.

    16 days after the first shock, CC is still 0.5 and FC loss during the day is more than usual, I'm doing a 3rd shock. obviously i'm not doing something correct. Does cartridge filter need to be cleaned after shocking? that'll be a pain b/c i just spent $165 cleaning it before algae started. Need advice please. And yes, using all chemical from this forum. Any additional reading about shocking besides the article in pool school? More details you can point me to? Thank you.
    Irregularly shaped IG pool with aggregates of squares and rectangles, spa overflows to pool
    21K gallon, Pebble tec, 450 sq ft, 125 GPM cartridge filter, 1hp pump, 1.5hp booster pump, Jandy heater,
    2 skimmers, 2 main drains, Hayward Navigator automatic vacuum connected to one of the skimmers

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    Re: persistent low grade algae?

    I'm sure that the experts will give further guidance, but my understanding is that 0.5 CC's is an acceptable number and that anything over that requires shocking.
    27' round AG
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    Re: persistent low grade algae?

    Was CC supposed to be 0.5 even when I had clouds of algae after brushing? Is my chemical bad?
    Irregularly shaped IG pool with aggregates of squares and rectangles, spa overflows to pool
    21K gallon, Pebble tec, 450 sq ft, 125 GPM cartridge filter, 1hp pump, 1.5hp booster pump, Jandy heater,
    2 skimmers, 2 main drains, Hayward Navigator automatic vacuum connected to one of the skimmers

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    Re: persistent low grade algae?

    Yes, it could very well be, your CC's are OK, I am going through an issue and my CC's have not been over .5 the entire time, just pay it no mind right now, the CC reading is one of the symptoms of something eating you FC. Add chorine when the sun goes down, test chlorine 30 mins later and then first thing in the morning. The overnight test will tell you if something is going on with your pool. As long as it is 1 or less loss of ppm, you're OK. If not, continue to shock and keep it their until you pass the overnight test and your water is clear.
    Vinyl 18x36 inground pool, cart 4030 filter, tristar VS pool pump, T-15 SWCG, raised pre-plumbed fiberglass spillover spa w/12 jets, tristar VS spa pump, Aqualogic pl-plus-16v
    McDonough (Ola), Georgia

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    Re: persistent low grade algae?

    The tests we use are designed as an aid to assist you in pool water management. Regardless of any test result, it is important to recognize the need for chlorine if you have algae in the pool.

    BBB is all about your understanding of what the various parameters are and what to do when they get out of whack.

    So, don't look for a black and white answer in every test result but rather look for clues and trends in your test results and understand what to do.

    Yes, we say the .5 CC is exactly the same as 0 CC's. In other words, it's inconsequential. Can you have algae in your pool and still register .5CC's? Absolutely! Many people experience that.

    One of the MOST important questions we ask a newbie is "How does your water look?" There is no test for that but their response can sometimes tell us more than any battery of tests results.
    Dave S.
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    Re: persistent low grade algae?

    Yes, you can check your filter to make sure it is clean: pool-school/cleaning%20pool%20filters

    Have you passed the Overnight Free Chlorine Loss Test?

    I agree w/what Richard said:
    Maybe you have something lurking behind the light, or in the filter, or even on pool toys or brushes. You could always toss all that stuff in and shock again
    Shock again and toss in all the toys and tools .

    Also, if it was my pool and driving me crazy, I'd shock to Mustard Algae level.

    Oh, and ditto Dave & BBailey
    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.

    ~ One should not use a sledge hammer to swat a mosquito. ~

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    Re: persistent low grade algae?

    Thank you for all your advice and comments.

    4:45 pm FC 14.5, CC 0.5 added FC to target of 16
    9:30pm FC 15.0, CC 0.5
    7:30am FC 15.0, CC 1.0
    repeated 8:00am FC 15.5, CC 0.5
    water still looks clear, tools in the pool. pump ran 7hr yesterday (2 more than usual). Now what? Thanks.
    Irregularly shaped IG pool with aggregates of squares and rectangles, spa overflows to pool
    21K gallon, Pebble tec, 450 sq ft, 125 GPM cartridge filter, 1hp pump, 1.5hp booster pump, Jandy heater,
    2 skimmers, 2 main drains, Hayward Navigator automatic vacuum connected to one of the skimmers

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    Re: persistent low grade algae?

    The other thing to do, if someone didn't suggest this already, is to brush the entire pool while it is at shock level. Pay special attention to places where algae could hide out from the chlorine, like the underside of ladders, etc.
    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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    Re: persistent low grade algae?

    Ok, will do. Con't to shock today?
    Irregularly shaped IG pool with aggregates of squares and rectangles, spa overflows to pool
    21K gallon, Pebble tec, 450 sq ft, 125 GPM cartridge filter, 1hp pump, 1.5hp booster pump, Jandy heater,
    2 skimmers, 2 main drains, Hayward Navigator automatic vacuum connected to one of the skimmers

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    Re: persistent low grade algae?

    Quote Originally Posted by irvinenewbie
    Thank you for all your advice and comments.

    4:45 pm FC 14.5, CC 0.5 added FC to target of 16
    9:30pm FC 15.0, CC 0.5
    7:30am FC 15.0, CC 1.0
    repeated 8:00am FC 15.5, CC 0.5
    water still looks clear, tools in the pool. pump ran 7hr yesterday (2 more than usual). Now what? Thanks.
    Have you considered bumping the pump run time to +7hrs for several days? When I battle anything, I run my pump upwards of 12hrs/day. Here in NC when pool temps get to 90 I have been known to run the pump 24/7 for awhile just to make sure nothing is going to grow.
    CaryB
    36 x 18 IG vinyl, 25K, 1 HP pump, sand filter
    1 skimmer, 2 returns, no main drain
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    Re: persistent low grade algae?

    Now what?
    Did you meet the criteria to indicate the shock process is complete?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: persistent low grade algae?

    When your pool is at normal (not shock) FC levels, then you can use a 25 ml sample size to be able to see if your CC is really just 0.2 or 0.4 ppm and not really 0.5 ppm. It's likely that it isn't really as high as you think.

    Be sure to expose your pool to sunlight since chlorine+sunlight helps break down most CC.
    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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