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Thread: Black Algae is kicking my butt

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    Black Algae is kicking my butt

    Good morning everyone. I have been lurking here and reading for a couple years to fix my pool challenges with great success, but currently my pool is running away from me. The water is clear but black algae rules. My chlorine is getting eaten so fast I can't keep up. As of this morning the test kit gives me the following numbers; Chlorine < .5, Ph 6.8, Alkaline 110, Hardness ~800 (maybe more, but the color change was not so exact), CYA < 100. So I know that my water is really out of whack, and I've already determined to drain the pool and start from scratch this winter. With the temperature over 100 at midnight in AZ I can't do much more at this point. I appreciate any help you guys can give me to get the numbers more into balance and do something with the black algae.

    Have a great day.
    13,000 gallon in ground plaster pool, sand filter, 1hp pump (don't know the flow rate), pool built in 2002.

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    Join Date
    Mar 2012
    Location
    Amarillo, Texas
    Posts
    341

    Re: Black Algae is kicking my butt

    Do you have a good test kit? That's the most important feature. Without it, it's very difficult for any of us on this site to give you much help. I started with black algae this summer and with a good test kit, the help of this board and a lot of elbow grease I probably have one of the prettiest pools in our area.
    18'x48" AG
    Pentair 1 1/2 HP Dynamo Pump
    Sand Dollar Sand Filter w/ Zeobrite
    Lil Shark Vacuum System
    Hard Plumbed

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    UnderWaterVanya's Avatar
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    Jun 2012
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    Mint Hill, NC
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    2,589

    Re: Black Algae is kicking my butt

    How are you testing? If strips - they are pretty useless for defeating problems. Get a good test kit (see pool school for more info) and more detailed test results.

    Without that you're going to have a really rough time fixing this.
    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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    Mod Squad Bama Rambler's Avatar
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    Jun 2009
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    SouthWest Alabama
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    Re: Black Algae is kicking my butt

    Welcome to TFP.

    How did you determine that it's black algae?
    Given your CH & CYA you need to drain a good bit of water but since you don't want to do that until the winter it's going to be very hard to "fix" that pool.
    If you're using a turbidity test for CYA then run the test by mixing half tap water with half pool water and double the result. Let us know what you get.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    linen's Avatar
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    Jul 2010
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    Twin Cities, MN
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    Re: Black Algae is kicking my butt

    Welcome to tfp, GEEKMEDIC
    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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    Re: Black Algae is kicking my butt

    I am using one of the recommended kits. It is the HCH kit. I know that is not the cadillac of kits, but I think it is sufficient for this purpose. I am afraid to drain the pool even half way because of the temperature right now. It is over 95 degrees 24 hours a day. I am willing to do pretty much whatever to fix the problem as long as it doesn't crack my plaster.

    Thanks
    13,000 gallon in ground plaster pool, sand filter, 1hp pump (don't know the flow rate), pool built in 2002.

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    linen's Avatar
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    Re: Black Algae is kicking my butt

    Quote Originally Posted by GEEKMEDIC
    I know that is not the cadillac of kits, but I think it is sufficient for this purpose.
    In general, and especially for your pool investment, it really isn't. You may be able to get by with it, but if you need to shock, you will be shooting in the dark. Also, you will have not clue about CC levels and you will run out of reagents for the tests you do have very quickly. We basically suggest it only for algae free pools that can be easily (and cheaply drained/refilled) and/or to bridge the gap until an appropriate test kit arrives.

    If you cya is close to 100, you may want to drain and refill. It would be best to repeat the test with 1/2 pool water 1/2 cya free water (such as tap water), then multiply the results by 2.
    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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    Re: Black Algae is kicking my butt

    I see the need for a good test kit, and it will be on order, but HCH was the one I could get my hands on instantly and it gave me some more information to work with as opposed to no information at all. At what temperature point can I drain the pool even half-way? It is my impression that I should not drain it if the ambient temperature is above 70 degrees. Is that incorrect?
    13,000 gallon in ground plaster pool, sand filter, 1hp pump (don't know the flow rate), pool built in 2002.

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