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Thread: Black Algae, High CYA, Dad just throws in more shock

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    Black Algae, High CYA, Dad just throws in more shock

    My dad has black algae in his pool and keeps throwing shock at it which doesn't do a thing. I've been educating myself on this board and use the BBB method on my pool and things are great. I keep telling him something is wrong; algae won't survive if the water chemicals are right. I read to rub triclor tabs on the algae which he did, and it helped. However, there is too much of it.

    Dad only tests ph and Clorine with a Wal Mart kit. The numbers show his pool is "in range". I keep explaining he wouldn't have an algea problem if his water was OK. I bought him a Wal Mark kit for $15 that test alk, hardness, CYA, chlorine and pH.

    Here are his numbers:
    pH 7.5
    Cl 2
    Alk 100-110
    Hardness 300
    Cya 110
    Concrete pool, approx 20,000 gal.

    What do you think about this?
    Drain the pool about 1/3 down. Take a Stainless Steel brush and dip it in Bleach and attack the black algae. Refill the pool.

    Would this help?
    14x30 Concrete Splash Pool
    DE Filter

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    frustratedpoolmom's Avatar
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    Re: Black Algae, High CYA, Dad just throws in more shock

    With a CYA of 100+, he would need to constantly maintain the FC at 7 minimum, 14 ideally. Thats why he has black algae, his chlorine is too low to prevent it and or kill it. And if he's at 2 now, that's akin to having zero.....

    Otherwise the numbers are fine. So yes, I would drain 1/3 of the pool, shock the pool according to the CYA chlorine chart -- link in my sig. Scrub and scrub to get the heads off the black algae. there's another recent thread about the very subject.....I'll try to find it.

    He needs to stop using the pucks. That's what led to the high CYA, and eventually the chlorine levels that used to be adequate no longer were, allowing the algae to take hold.

    Black algae is nasty, tuff stuff. It is resistant to chlorine, it takes really high levels and alot of scrubbing to get thru to the under-layer so that the chlorine can kill it. The outer layer is like a tough skin of armor and it's hard for chlorine to penetrate it.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    frustratedpoolmom's Avatar
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    Re: Black Algae, High CYA, Dad just throws in more shock

    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Re: Black Algae, High CYA, Dad just throws in more shock

    Not knowing about your water table, I wouldn't drain anymore than one third from the pool.

    Before using the stainless steel brush, I would get a cheap garden sprayer (used for weed killer from like Lowes) and spray with straight 6% OR 12% CHLORINE any algae that was exposed above the water line(after you drain out some water) let it sit for a couple of minutes then brush. Remember, anything you brush is just going to fall into the pool. Your going to have to brush more than once or twice; even after the water level is back to normal. Also, once the pool level is back to normal, your father is going to have to run his pump and filter 24 hours a day while the chlorine level is high to get the dead algae out of the water.

    Your CL of 2 isn't any good. You have to raise it alot higher to even have a chance to kill the algae. When you raise the chlorine level, you will have to hold the chlorine level for a couple of days to have a chance to kill the algae. ( I won't tell my thoughts on how high to take the FC level cause I'm not wearing my flame suit. )Make sure you do some reading in the pool school threads; it will help you with your pool along with your father's pool. Also, a better test kit that shows FC and CC would help. I would think that your father's CC in his pool is high.

    I've never used or seen used a pressure washer to due pool sides; so you have to see if someone will answer this thread that as used one, but it is a thought.

    Draining water from the pool will help lower the CYA level which is high.
    Hotrod30

    20 X 40 foot vinyl Borates and Salt Pool
    Rolachem Chlorine Feeder
    Hayward 27 inch sand filter with 80 lbs of pea gravel
    Jacuzzi Splash Pak SP55 DE filter in parallel
    Pentair VF3050 pump

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    JasonLion's Avatar
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    Re: Black Algae, High CYA, Dad just throws in more shock

    You should also look at where the CYA is coming from. Many common "shock" products contain dichlor, which contains CYA. Shock with dichlor and your CYA level goes up quickly.
    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: Black Algae, High CYA, Dad just throws in more shock

    I know my dad is shocking the pool with:
    Multi-functional chlorinating granulars (sanitizer-shock-stabilizer) 55.5% chlorine which he purchased from Sams. I do think the pucs he uses are DiChlor.

    After draining the water down some, I will also try to get him to use bleach.

    Thanks for all the help.
    14x30 Concrete Splash Pool
    DE Filter

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