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Thread: Algaecide and shock calculation help - green pool

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    Algaecide and shock calculation help - green pool

    Opened my pool last weekend and it was super clear. It turned green at some point this week, even though the water was only 52 degrees. It was too cold to run my SWCG and I didn't worry about it cause I thought water was too cold for algae to grow... gotta learn some lessons the hard way I guess.

    Anyway, just wanted some advice on my calculations so that I do this right and minimize the monetary damage as much as possible.

    First of all, the pool store sold me on a strong algaecide, some type of polyclot that is strong, 60%, I guess I need to use that to break up the algae so that it doesn't continue to produce more algae even after that algae bleached out. Is this accurate? I don't see this mentioned in pool school under the fighting algae section. Thinking maybe they are just selling me on an expensive product?

    Here are my #s. (tested at pool store) The chlorine was brought up to this level from zero by adding 7 lbs of shock last night.
    42,000 gallon gunnite pool
    FC = .6
    TC = 1.0
    ph = 7.8
    alkalinity = 270
    CYA = 40

    So according to the CYA/Chlorine chart I'm aiming for a shock level of 24. (or under, it doesn't list 40 CYA in the chart)

    The pool calculator is telling me I need 873 ounces of 14% chlorine, (the tested level of the chlorine I just bought at pool store)

    First, should I add 1/2 - 3/4 gallon acid to bring my alkalinity down and my ph down a bit first?
    Do these #s look right? Am I doing anything wrong?
    Should I add the algaecide mentioned above?
    Should I wait till evening to add liquid chlorine to get the maximum effectiveness? It's overcast here today so sun won't suck out chlorine too much. Or should I just get the chlorine in their ASAP?


    Thanks in advance for the help

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    Smykowski's Avatar
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    Re: Algaecide and shock calculation help - green pool

    Welcome to the forum.

    Once algae is growing, algaecide isn't much help. It will do a bit of killing, but it's much much more effective as a prevention. Polyquat 60 is good stuff, but I wouldn't put it in the pool because it really won't be effective at this point.

    All of my advice comes with the giant qualification that it depends on those pool store tests being accurate (which we in general believe to be a false statement).

    If the pool is green you need to SLAM the pool. You need the precision of an FAS-DPD test to complete the SLAM correctly.

    Step 1 would be to lower pH to 7.2-7.4. Ignore TA for now.

    Without the SWG running, you would treat your pool as a manually chlorinated pool. Your SLAM level would be 16, and I'm getting about 8 gallons of 8.25% bleach to reach SLAM level.

    What are the ingredients in the "shock" product you added? Do you have a reading for your CH level?
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    Re: Algaecide and shock calculation help - green pool

    thanks for the welcome

    Calcium hardness is 210.

    I just added 3/4 gallon acid to bring ph down. How long should I wait before adding chlorine?

    I feel you on not trusting the pool store, but I tend to trust this pool store's calculations more than most. As they use both a computer to read the strips and do the whole chemistry experiment as well.

    The shock was bought at walmart, hth brand, 47% calcium hypochlorite, 53% "other ingredients"

    Looks like I need a FAS-DPD test, The sticky lists three, are any of these 3 the cheapest option for me? The: TF Test Kits TF100, Taylor K-2006 kit, and Leslie's Chlorine FAS-DPD Service Test Kit

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    Re: Algaecide and shock calculation help - green pool

    Computers and strips are the big loud siren we hear when we see that. I'd rather see a pool store that uses drops than strips and/or a computer.

    The shock you bought will add CH, but your CH is a little on the low side (if it was measured correctly, CH is one of the harder tests to get right). Don't use any Dichlor or Trichlor products since your CYA is already where it needs to be. Liquid bleach/liquid shock is what is recommended at this point. Plain bleach works just fine, not splashless, outdoor, or scented bleach.

    You can get the FAS-DPD test on its own from tftestkits.net if this is the only test you need. Otherwise the TF-100 is the nicest kit on the market.
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    Re: Algaecide and shock calculation help - green pool

    The TF-100 kit is your cheapest option. Not because it costs less, because it doesn't. It's the cheapest because it will save you the most money on poor results from a pool store and has all the ingredients in appropriate quantities for testing, especially when SLAMing your pool.

    As soon as you have it ordered, read more Pool School. Then read some more. Not just about getting rid of algae, but everything.

    Also... I've developed a distaste for the word "shock." Shock is like a 10 second horror movie where a ghost comes out and says BOO and then the credits roll. If you want to scare the **** out of algae, it has to be a feature-length horror film SLAM complete with recurring nightmares.
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    Re: Algaecide and shock calculation help - green pool

    That shock was put in last night already. Before the CH test today.

    Right now I have liquid bleach/shock bought at the pool store. They are saying they tested it a few days ago and its at 14% chlorine.

    Looks like online is my only option for the FAS-DPD kit which doesn't do me much good right now. Shouldn't I attack this problem now instead of waiting for test kit to arrive in mail? Won't the algae grow in the meantime? Should I just use visual green test?

    Pool calculator is telling me to add 4 gallons of 13.5% chlorine. Pool store told me to ad 12. LOL. I think I'll add in 4 gallons and wait an hour as instructed in the sticky.

    How long after adding acid should I wait to add the chlorine?

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    JasonLion's Avatar
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    Re: Algaecide and shock calculation help - green pool

    An hour for the acid to mix in is plenty.
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    Smykowski's Avatar
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    Re: Algaecide and shock calculation help - green pool

    You can retest pH 30 min after adding acid.

    Our general recommendation is 30 min between chemical additions.

    As for what do to without a FAS-DPD kit, not sure what to tell you. You can guestimate if you have a color comparator test for chlorine, but I'd be very leery of using strips to get any information during a SLAM.
    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: Algaecide and shock calculation help - green pool

    Thanks for all the help, I'm amazed at how helpful this community is.

    Quote Originally Posted by Smykowski View Post

    As for what do to without a FAS-DPD kit, not sure what to tell you.
    Hmmmm.... with the water only at 54 degrees can my algae problem really get much worse while I wait a week or whatever for kit to arrive?

    Or should I just start slamming it and base everything off how not green the pool looks as indicated in the sticky?

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    Re: Algaecide and shock calculation help - green pool

    I found a local test kit, she claims it tests for FAS-DPD... its a Bioguard brand. Anyone familair with it? Google is being inconclusive. I'm seeing 50 Test Tablets of DPD #1 in the item description when I google it.

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    Smykowski's Avatar
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    Re: Algaecide and shock calculation help - green pool

    That's not it. That's the DPD test, and most pool stores that sell it will tell you (out of ignorance) that it's the FAS-DPD test.

    No one here has found them in a retail store, with the exception of some Leslie's commercial warehouses.
    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
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Re: Algaecide and shock calculation help - green pool

    I know you are eager ... but if you order the TF-100 he ships really fast and you will have peace of mind that you are getting the right kit!
    SwimNPlay AG 15x33 oval 48" high 12k gallons - Used pool set up July 2013
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    Mod Squad jblizzle's Avatar
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    Re: Algaecide and shock calculation help - green pool

    I am not familiar with that test kit to know if it is truly the FAS-DPD test ... I would get the Tayler version in the TF-100 or the K-2006.

    Pool stores tend to like the nuclear option as you found ... just toss in this ridiculous amount of chemicals and hope for the best ... oh and don't blame them if you end up damaging the pool or equipment due to their recommendation.

    We prefer the safer and more scientific approach.

    - - - Updated - - -

    Where are you located? On the West coast, poolsupplyworld.com might get the TF-100 to you quicker.

    I placed an order with them a few weeks ago ... the 3 items I bought shipped out of 3 different places in the country and got to my door surprisingly quickly.
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    Re: Algaecide and shock calculation help - green pool

    AprilNC I am also new to this forum. I have been installing an AG pool this year. I purchased the TF-100 kit and the stirrer. I live near Augusta Ga and it was here in two days. Amazing!!! It really makes the test easy to run and get the correct results. When I had earlier pools I purchased the kits and strips from wal-mart, etc and could never get dependable results. The FAS-DPD test kit checks for very high chlorine levels. The common kits only test to about 5 - 8 PPM chlorine and to get rid of the algae you need much higher levels of chlorine than they can test.
    Good Luck.
    Gerry
    27' x 54" AG Salt Water Pool Installed 2014, Hayward 23" Sand Filter, 1 HP 2-Speed Power-Flo Matrix Pump, AQ-TROL SWG, TF-100 Test Kit

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    Re: Algaecide and shock calculation help - green pool

    I'm in Indiana.

    Yes, I'm eager... so I of course added 5 gallons of 13.5% about an hour ago. I just used a test strip... I know, its just a strip but its reading at 10+ still. I just brushed it as well. I'm not seeing any difference in color yet.

    Local pool store sells the Taylor K-2006 for $79.99, think I should go swoop it up? Only 12 bucks more than the TF-100, am I getting everything I need with that?

    So if I'm reading this sticky right I just want to keep chlorine at about 16 until algae clears up?

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    Smykowski's Avatar
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    Re: Algaecide and shock calculation help - green pool

    That's a bad deal. TF100 is cheaper, and will give you more reagents for the tests you need most.
    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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    Mod Squad jblizzle's Avatar
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    Re: Algaecide and shock calculation help - green pool

    I would not. I would order the TF-100 with the XL option. If you buy the K-2006, you should also look at how much it will cost to add more R-0780 and R-0871 because you are going to run out very quickly before you finish the SLAM process. Oh and you get about half of the CYA tests in the K-2006.
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    Re: Algaecide and shock calculation help - green pool

    Ok.

    I ordered the TF-100, hope it gets here soon.

    Meanwhile I put in another 2 1/2 gallons of 13.5% liquid chlorine about an hour ago. The test strips are still 10 + in terms of FC.

    I think the pool is a little bit clearer. I can kinda see the main drain now, I couldn't at all before.

    Should I keep putting chlorine in? Or throw in the towel till test kit gets here and count the 7 1/2 gallons I've thrown in already as a learning lesson.

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    Mod Squad jblizzle's Avatar
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    Re: Algaecide and shock calculation help - green pool

    I would wait until you can register something on the strip and then use PoolMath to figure out how much your should add to get back to SLAM level (assuming your CYA is 40ppm).

    You do not want to have the FC be too high as that can cause issues and is just a waste since more is lost to the sun.
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    Re: Algaecide and shock calculation help - green pool

    Quote Originally Posted by jblizzle View Post
    I would wait until you can register something on the strip and then use PoolMath to figure out how much your should add to get back to SLAM level (assuming your CYA is 40ppm).

    You do not want to have the FC be too high as that can cause issues and is just a waste since more is lost to the sun.
    Makes sense... too bad the test strips are so inaccurate and hard to read. I see why the test kits are such a hugely important tool.

    How long does this process take usually before you start seeing results? The sticky makes it seem like you'll start seeing it clear up during the course of a day.

    For a point of reference here is what pool looked like when I started... it looks pretty similar right now:


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