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Thread: How Long to Treat Algae

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    How Long to Treat Algae

    Greetings, all,

    I came across this site after doing some research into my pool problems. It's a great resource! I'm following one of the guides, but was wondering how long it should take to clear up a severe algae bloom when keeping the pool in a constant shock condition. Below are some additional details:

    I took over an above ground swimming pool that is 24' round, so I estimate about 13,500 gallons of water. It was not covered during the winter and we're now 1.5 months into summer. So the water was a dark green and you cannot see below the surface very well. I've been following the Turning Your Green Swamp Back into a Sparkling Oasis article, but was wondering how long it should take to clear up.

    I was using test strips, but after reading some other articles on this website, I recently ordered Taylor K-2006 Test Kit, but it won't arrive for a few days. I realize the inaccuracy of these, but my current numbers are as such:

    FC: At least 10 ppm (current test kit/strip's max).
    pH: 7.2
    TA: 60
    CH: 240
    CYA: 40

    To shock the pool, I'm using Leslie's Power Powder Pro (73% Calcium Hypochlorite). I know regular bleach is the same thing, but at 50 lbs, it was only about $2 a lb, which was about what I was spending on bleach (which is also significantly more difficult to handle (1.42 gallon jugs vs. 1 50 lb bucket). Every day, I've been adding 1 lb (2 cups) of the PPP and I check the FC around twice a day to ensure it hasn't dropped. My FC test only goes up to 10 ppm, so I can't be sure if it's much higher than that and on a day to day basis, it doesn't really drop. That somewhat concerns me since I would expect the FC to drop as it kills of the algae, and while I feel I should let the FC drop some before adding more, I'm also afraid to let it bounce back and forth (as per some of the articles I've read). I'd estimate that I've kept the pool fully shocked for the last 6 days or so. The water does seem less dark than before, but you still can't see the bottom. I try to brush the bottom and sides, but because the water is so dark, it doesn't seem like it's helping much (I basically push the brush along the floor, but I can't really see anything happen). However, after the initial treatments (and even to today), I do see the white/grey dead algae floating on the surface, so that is progress. I also wonder if my pool pump is operating optimally. It's around 10 PSI.

    Can anyone provide some guidance? How long should this process take before I can at least start to see the bottom of the pool? Should I continue to add 1 lb of the PPP daily even when the FC is high? Shouldn't the FC level be dropping from day to day in a severe case like this? Thanks.

  2. Back To Top    #2
    JasonLion's Avatar
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    Re: How Log to Treat Algae

    Welcome to TFP!

    It can take one to three weeks assuming nothing goes wrong. After the first couple of days you should be seeing an visible improvement each day.

    With CYA at 40, shock level is 15 to 16. Having FC at 10 isn't good enough. What test have you been using to measure the FC level?

    How has your filter pressure been behaving? With the water full of algae, the filter pressure should be going up fairly rapidly. What kind of filter do you have? Have you needed to backwash/clean the filter?

    Also, have you removed everything you can from the bottom of the pool? It is crucial that you get all of the leaves and debris out of the pool that you possibly can.
    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: How Log to Treat Algae

    Your FC is too low per this link pool-school/chlorine_cya_chart_shock, according to the chart you need to be at least @ 16ppm on your shock level. It will be difficult untill you get a good test kit that can test at higher Fc levels. If you cvan test hourly to keep Fc up as it should be eaten fairly quickly by the algae and organics in the pool.
    You need to remove all debris from the pool, and will need to clean your filter frequently.
    Welcome to TFP!
    EDIT: Jason types faster than I do!
    17,000 gal, IG Gunite Diamond Brite plaster Kidneybean,w/7x11 tanning ledge& 3x5 swimout bench,244T 300lb Hayward Pro high rate sand filter(63 GPM) , Hayward 1Hp Super Pump w/3/4 hp booster pump, Polaris 280, Laars Lite 2 175k N/G Heater, Tf-100, Speed stir

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    Re: How Long to Treat Algae

    Sorry, I should have been clear on the FC. I've been using some test strips and a HTH 6 Way Test Kit, which only read up to 10 and 5 FC PPM respectively, so that is the least amount and not the actual level. Once my Taylor's K-2006 Test Kit arrives, I can more accurately measure the FC and and start to measure the CC.

    I don't know if my water pump is actually behaving or performing as intended. It's usually at 10 PSI, but if I recall correctly, the old owner said it worked around 15 in the previous year(s). At least in my casual obersation, it does appear to have enough suction for vacuuming. I also broke it down yesterday to ensure there were not any leaves caught in the impeller. I've been backwashing every few days, but it only drops 2-3 PSI when I do that and it returns back to 10 within a day or two afterward. It's a sand filter.

    I wasn't sure how to get check for leaves and debris since I couldn't see the bottom, but I did just read about using a leaf hook/catcher (I forget what it's called, but I have one), so I'll definitely try that.

    If you cvan test hourly to keep Fc up as it should be eaten fairly quickly by the algae and organics in the pool.
    That was my expectation, but it doesn't seem that way. I'm guessing that my FC is up enough already that it's never dropping below the 10 ppm (the test strip's max), as that is what it is each morning before I add another pound of the PPP. Do you think I should continue to add a pound each day, at least until my new test kit arrives (thus allowing me to more accurately maintain the 16 ppm FC shock level)?

    I probably should have done this from the start, but I'll also start taking pictures every few days so I can at least compare for visual differences.

  5. Back To Top    #5
    JasonLion's Avatar
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    Re: How Long to Treat Algae

    It sounds like you are having a problem with either the filter or the main valve. If the pressure only goes up 2 psi and then stops going up, water might be finding a way to bypass the filter once it gets to that pressure. I suggest checking the spider gasket and/or o-rings on the main valve and also resettling the sand bed on the filter, described here.
    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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