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Thread: Recurrent Algae and High Phosphate Levels

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    Recurrent Algae and High Phosphate Levels

    Hello all-

    I know this topic has been beaten to death, but I thought I'd try to pick some brains in a fresh thread.

    My pool, which is usually not prone to algae bloom, and chemically balanced pretty darn well according to my own tests and that of two separate local pool stores, has been getting frequent surface algae. Its beginnings seem to coincide with my landscapers spreading some nice fertilizer into my pool a few weeks ago.

    My Phosphate level is at 2500 according to at least two tests, and repeated scrubbing, backwashing, and shocking has not worked; the green patched return in a day or two.

    I have reservations about using things such as "Green to Clean" and "Phos-Free" and frankly, don't need to empty my wallet right now as we are on a tight budget.

    I have a 26,000 gallon vinyl-lined pool, live on Long Island, and the pool gets all-sun, all day.

    I am sure you folks may have other questions for me, so ask away and thanks.

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    Patrick_B's Avatar
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    Re: Recurrent Algae and High Phosphate Levels

    Welcome to TFP!

    The reason you keep seeing Algae is because you are or have been low on Free Chlorine. You may have phosphates in your pool, but they can easily be made completely irrelevant with proper levels and maintenance of free Chlorine residuals. Dead or non existent Algae cannot utilize them as nutrients. It's really that simple.
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    Re: Recurrent Algae and High Phosphate Levels

    Thanks Patrick. That is what is so puzzling. My FC levels are actually pretty much within range, so I am pulling what's left of my hair out trying to figure this out.

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    Re: Recurrent Algae and High Phosphate Levels



    - - - Updated - - -

    Can you post us your most recent test results? Specifically CYA, pH, CH, ALK, FC, and CC.
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    Re: Recurrent Algae and High Phosphate Levels

    Welcome to the forum. We can help fix your pool. Everything we do begins and ends with test results. Can you post your current test results? Not pool Store......we find there testing to be not much help.
    Dave S.
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    Re: Recurrent Algae and High Phosphate Levels

    Thanks folks. My kit is pretty limited to Ph and chlorine, and then I have some fresh strips. It's difficult to give pinpoint results but I will do what I can to furnish you with something useful.

    - - - Updated - - -

    BTW, what is CC?

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    Re: Recurrent Algae and High Phosphate Levels

    I can't produce CYA and CH results but the following is what I see:

    FCl = @2
    Alk = @100
    pH = 7.6
    Assuming CC is combined chlorine, and if that is the yellow part of the "drop test", it's around 2 or so, but I'm not sure this is what you're after.

    CYA from pool store is 50 and CH is 200

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    Re: Recurrent Algae and High Phosphate Levels

    Welcome to TFP. With some reading and some questions and answers you're going to be on your way to a clear pool. Soon you'll see that your thread topic could have read "Recurrent Algae due to Improper Chlorine/CYA Ratio."

    It's a lot to learn at first but everything here is backed up by science.

    Glad you saved your money and didn't buy the pool store potions. What you need the most right now is a proper test kit. You'll need a kit that can test chlorine levels over 10, CC (Combined Chloramines), CYA(Cyanruic Acid aka stabilizer, conditioner) pH, Total Alkalinity, Calcium Hardness.

    There aren't many that test everything we're going to be asking about and you usually can't find them locally. I use a TF-100. There is also the Taylor K-2006. Both of those have everything you'll need to take control of the pool and will save you money in the long run because you'll know exactly what is in your water and only add exactly what you need. No more "take 2 of these and call me in the morning" trips to the pool store.



    CC is combined chlorine. it's (non technical explanation) a measure that shows if your chlorine is working on killing something in the pool. A byproduct of the chlorine sanitizing process. If you click on pool school and read the ABCs of pool chemistry you'll get some better explanations.
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    Re: Recurrent Algae and High Phosphate Levels

    CC is Combined Chloramines. It is usually positive when you have organics in you pool. It is what makes a pool smell like chlorine.
    39YO 13K gallon former SWAMP/MONEY PIT, concrete bottom/Fiberglass Walls, Ecotech VS pump, Hayward Sand Filter, Dolphin DX5 Plus, Loop-Loc safety cover and YES, I have a TFT-100 test kit!

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    Re: Recurrent Algae and High Phosphate Levels

    Quote Originally Posted by Swataz View Post
    I can't produce CYA and CH results but the following is what I see:

    FCl = @2
    Alk = @100
    pH = 7.6
    Assuming CC is combined chlorine, and if that is the yellow part of the "drop test", it's around 2 or so, but I'm not sure this is what you're after.

    CYA from pool store is 50 and CH is 200
    You definitely need to get some chlorine in your pool if you FC is 2 and your CC is 2 as well. Any chlorine that you are adding now is being consumed by the algae that is in your pool. Then, you should read how to SLAM and about the OCLT. Both of these pages will help you gain the knowledge required to rid the pool of algae. Then, the Pool Calculator will guide you in how much Chlorine you need to add to the pool to bring it to shock level.

    Also, test strips are not very accurate as a whole and from one strip to the next. Taylor makes the test kits that this forum recommends but in the interim, there are five and six way test kits that you can purchase locally that will at least give you a better idea of what you are working with.
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    Re: Recurrent Algae and High Phosphate Levels

    you are lucky to have found this website. we are going to save you a ton of money. only thing we are going to push you to buy is the proper test kit. you might balk at the $60-70 cost of that, but its going to last you a long time and its going to let you get your pool crystal clear and KEEP it crystal clear. no weekly shock, no fancy stuff from the pool store. all the stuff you will need going forward you can buy at a big box store and save ton of money. you will be buying a lot of bleach though but compare to pool store hocus pocus, that's cheap.

    just remember, the people here making recommendations have ZERO financial gain in anything recommended. everything here is recommended based on science, not the maximize profits method employed by pool stores.

    get the test kit, it will be the best money you spend. when you compare the taylor 2006C to the TF-100, the TF-100 is a lot better deal since you get so much more.

    - - - Updated - - -

    Quote Originally Posted by Swataz View Post
    Thanks Patrick. That is what is so puzzling. My FC levels are actually pretty much within range, so I am pulling what's left of my hair out trying to figure this out.

    you will find out that your chlorine levels are not within range. the pool store probably tells you to keep it between 1 and 3ppm? well, the truth is you determine your chlorine level based on your CYA level. its critical that you have an ACCURATE CYA reading. pool stores do not test it correctly, you need one of the two recommended kits to determine.

    for example, my pool has a chlorine level of around 9ppm...but I have a lot of CYA (Stabilizer). my pool with 9ppm is a lot less harsh (and lower relative chlorine level) than a pool with 2ppm with no stabilizer.
    Dan
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    Re: Recurrent Algae and High Phosphate Levels

    Welcome to TFP! Wait that says 2013! Have you been lurking?

    All you need is a Taylor K-2006 test kit or a TF100 test kit from TFTestkits.net. Once you get one of those we can help you clear up your pool once and for all.

    Once you know your CYA level you can set the right chlorine level for your poo using the Chlorine CYA Chart. It is important to always keep FC at target level and never let it drop below minimum or algae will grow and the pool will be unsanitary.

    Read this first,
    Pool School - Getting Started
    And then this
    Pool School - ABCs of Pool Water Chemistry

    Once you get a test kit with CYA test and FAS/DPD chlorine test you can Pool School - SLAM - Shock Level And Maintain your pool and get rid of the algae.

    More on test kits here, Pool School - Test Kits Compared
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    Re: Recurrent Algae and High Phosphate Levels

    Quote Originally Posted by Swataz View Post
    Thanks Patrick. That is what is so puzzling. My FC levels are actually pretty much within range, so I am pulling what's left of my hair out trying to figure this out.
    As you will find from reading the Pool School on this forum, the FC level alone means absolutely nothing except to tell you how much chlorine you have in reserve so that you don't run out. It has absolutely nothing to do with the active chlorine level in the pool that prevents algae growth, kills pathogens, and oxidizes bather waste. The active chlorine level is proportional to the FC/CYA ratio so it is absolutely critical that you have accurate FC and CYA numbers.

    We have found that most test kits do not give accurate results and that is particularly true for many test strips. Most pool stores are no better in spite of some that use presumably good kits or equipment. The temporary help they hire for the summer are not usually well-trained and there is very little incentive for a pool store to give you accurate results because their goal is to make money and the way they do that is by selling you more product.

    So you need to save up to get yourself a proper test kit. In the long run you'll save more money by not having to buy anything extra from the pool store. No algaecides, phosphate removers, clarifiers, flocculants, enzymes, weekly shock, etc. Just chlorinating liquid or bleach and some acid.
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    Re: Recurrent Algae and High Phosphate Levels

    Wow, that is some service! Thanks, everyone!

    I will be getting the TF100 methinks. It is better to invest in a nice kit like that instead of putting that $80 toward insanely marked-up chemicals. As it is, I have already graduated to the 13 lb bags of baking soda for alkalinity issues.

    A quick question until I have some time to devote to this and also until I get the kit - would using last year's 3" tabs in my chlorinator have a massive effect on FC and CYA levels? Thanks!

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    Re: Recurrent Algae and High Phosphate Levels

    For every 10 ppm Free Chlorine (FC) added by Trichlor (the 3" tabs you have), it also increases Cyanuric Acid (CYA) by 6 ppm. So unless your CYA is low and you want to raise it slowly, the Trichlor isn't the chlorine to use. One 8-ounce 3" puck (some weigh less) in 26,000 gallons raises the FC by 2.1 ppm and the CYA by 1.3 ppm. That's roughly one day's consumption of chlorine.
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    Re: Recurrent Algae and High Phosphate Levels

    If trichlor isn't the chlorine to use, what other options are out there?

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    Re: Recurrent Algae and High Phosphate Levels

    Chlorinating liquid or regular unscented bleach (both are sodium hypochlorite and differ only in concentration) is the primary source of chlorine because unlike Trichlor and Dichlor it does not increase the CYA level and unlike Cal-Hypo it does not increase the CH level. There is also lithium hypochlorite that similarly does not have CYA or CH side effects, but it is very expensive so we don't normally recommend it, but technically it would also work. Of course, there is also chlorine you can get from a saltwater chlorine generator.

    The main downsides to using chlorinating liquid or bleach are that they are less concentrated forms of chlorine so are heavier to carry (i.e. you use more weight of them to get the same FC level) and you need to add chlorine to the pool every day or two. That is, you don't have slow-dissolving tablets you can fill in a larger feeder so only add more weekly or perhaps twice a week.
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    Re: Recurrent Algae and High Phosphate Levels

    Good move on getting a kit! Now you'll be able to know for sure, and take the correct action. Let us know when you have a fresh set of numbers, and we can help put you right.
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