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Thread: High TC but green algae still appearing

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    High TC but green algae still appearing

    Hi everyone, thanks to all of you, my water is great. However I am trying to help a friend. She has a 10000 Gallon Vinyl Pool. She has green algae on the sides of her pool and a little on the bottom.

    I tested her pool and her levels are:
    FC 16
    CC 1
    TC 17
    T/A 180

    With her FC at 16, I wouldn't think she should have any algae, becuase it has maintained that level for over 2 days.

    Any suggestions?

    Thanks!
    24" Round Above Ground 52" high
    Jacuzzi CFR 100 Platinum Filter

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    Smykowski's Avatar
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    Re: High TC but green algae still appearing

    Shock level is dependent on CYA level. Can you post a full set of results?
    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: High TC but green algae still appearing

    Quote Originally Posted by Smykowski
    Shock level is dependent on CYA level. Can you post a full set of results?
    I knew I forgot something! I will get the CYA Level tonight...

    Thanks!
    24" Round Above Ground 52" high
    Jacuzzi CFR 100 Platinum Filter

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    Re: High TC but green algae still appearing

    Ok, here are the reults:
    FC 20
    CC 0
    TC 20
    PH 7.5
    T/A 170
    CYA 120

    In checking the Pool Calculator, it looks like the best thing is to drain and refill about 60% of the water. Shock level would need to be 28!

    What do you think?

    Thanks!
    24" Round Above Ground 52" high
    Jacuzzi CFR 100 Platinum Filter

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    Mod Squad jblizzle's Avatar
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    Re: High TC but green algae still appearing

    The CYA could be well above 120ppm so changing even more water out may be needed.

    But, you do understand why the pool is green. With the high CYA, FC likely dropped too low at some point and now the FC is still well under the shock level.

    How are they chlorinating?

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    Re: High TC but green algae still appearing

    Thanks for the reply. Yes, I agree, I told her it is too high and that she needs to drain the pool. She is using granular chlorine and shocks every 2 weeks! I told her to start using this forum and to switch over to Bleach..

    In the meantime, if she adds bleach to get up to a shock level, will it decrease her cya, or is draining the only way to do that?
    24" Round Above Ground 52" high
    Jacuzzi CFR 100 Platinum Filter

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    Mod Squad jblizzle's Avatar
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    Re: High TC but green algae still appearing

    PARTIAL drains are you only option to lower CYA. Fully draining could ruin the liner.

    No point in adding any chems until you get the CYA down.

    Likely the granular chlorine AND the shock were raising the CYA. Maybe you should re-do the CYA test with a 50/50 mix of pool and tap water to start and then double the result to see how high it REALLY is.

    I would not want them to replace 50% of the water and then you retest and they are mad at you that the CYA is still over 100 ... better to have full disclosure to start that multiple water replacements may be required.
    Jason, TFP Moderator
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    Re: High TC but green algae still appearing

    That sounds like a great idea!

    I will test using the 50/50 method.
    24" Round Above Ground 52" high
    Jacuzzi CFR 100 Platinum Filter

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    Re: High TC but green algae still appearing

    You're on the right track, reduce the stabilizer level, brush the algae, and the chlorine will solve the problem.
    In the industry, CSP (Certified Service Professional) by the NSPI and it's successor the APSP. My company services over 600 pools every year. I think the practices regularly espoused on this forum (especially the BBB method) are outstanding; however my comments will be often oriented towards the goal of getting it done, and getting it done right now!

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    Re: High TC but green algae still appearing

    Quote Originally Posted by Jimh64
    Ok, here are the reults:
    FC 20
    CC 0
    TC 20
    PH 7.5
    T/A 170
    CYA 120
    So you can have active growing algae and still get a CC of 0? Wow... I didn't know that. I'm new to this and still learning but that was a shock.
    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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    linen's Avatar
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    Re: High TC but green algae still appearing

    Quote Originally Posted by UnderWaterVanya
    So you can have active growing algae and still get a CC of 0?
    Yes, that is part of the reason there are three criteria in the shocking process (see my sig), any one of them is an indication of organics.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    UnderWaterVanya's Avatar
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    Re: High TC but green algae still appearing

    Quote Originally Posted by linen
    Quote Originally Posted by UnderWaterVanya
    So you can have active growing algae and still get a CC of 0?
    Yes, that is part of the reason there are three criteria in the shocking process (see my sig), any one of them is an indication of organics.
    Understood. I'll hopefully get to the OCLT tonight. The water is looking great. I ran it up to about 15ppm (again no time to validate the exact value after adding bleach) and this afternoon on a hot sunny day it was only down to 12ppm so I am hopeful.
    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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