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Thread: New Bloom of Algae, What am I doing wrong?

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    New Bloom of Algae, What am I doing wrong?

    This is my second year managing an inherited old pool that needs a lot of updating. Thanks to all that give of their time on this website I have been able to quickly clean it up and use it and when I make mistakes can easily bring it back to crystal clear. I monitor the chlorine level at least 2 X a day and if the FC is below my target of 4 in the am dosing, I target for 5 for that dose as my CYA is only 30 and the sun can consume the chlorine fairly fast even with the solar cover on. However I know the FC has not gone below 2.5. My new problem is that yesterday while dosing I noticed green algae on the floor of the skimmer intake, I took the solar cover off and while I could see the bottom it had lost it's sparkle. I brushed (which I haven't done for while because I purchased a robot cleaner and run 2 cycles a day which I thought would be better than brushing) and saw a little green cloud so I started a slam and while I am sure it will come back quickly, I am curious as to why the algae bloom started and even more, why would it concentrate on the floor of the skimmer intake where circulation is sure to be good.
    My numbers are:
    FC=13 (before slam 4)
    CC= < .5
    PH= 7.5 (actually color between 7.5 and 7.2)
    TA= 80
    CH= 100
    CYA= 30
    28,000 gals (20 x 40), IG, vinyl, Hayward Sand Filter, old Hayward
    Super pump (not sure of HP secondary to corrosion of label),

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    Wildcat's Avatar
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    Re: New Bloom of Algae, What am I doing wrong?

    Quote Originally Posted by Pool Amateur View Post
    This is my second year managing an inherited old pool that needs a lot of updating. Thanks to all that give of their time on this website I have been able to quickly clean it up and use it and when I make mistakes can easily bring it back to crystal clear. I monitor the chlorine level at least 2 X a day and if the FC is below my target of 4 in the am dosing, I target for 5 for that dose as my CYA is only 30 and the sun can consume the chlorine fairly fast even with the solar cover on. However I know the FC has not gone below 2.5. My new problem is that yesterday while dosing I noticed green algae on the floor of the skimmer intake, I took the solar cover off and while I could see the bottom it had lost it's sparkle. I brushed (which I haven't done for while because I purchased a robot cleaner and run 2 cycles a day which I thought would be better than brushing) and saw a little green cloud so I started a slam and while I am sure it will come back quickly, I am curious as to why the algae bloom started and even more, why would it concentrate on the floor of the skimmer intake where circulation is sure to be good.
    My numbers are:
    FC=13 (before slam 4)
    CC= < .5
    PH= 7.5 (actually color between 7.5 and 7.2)
    TA= 80
    CH= 100
    CYA= 30
    In my opinion you are cutting your FC levels too close. If your CYA measurement is off, maybe it is 40, hardest measurement to do, you could be under FC levels needed.

    And why measure FC twice a day? Bring it up to max and let it drift down to mid point or minimum over a couple of days. While some will counter that you lose more at higher levels it is not that much and you are safer being at high end of range.

    Only three ways algae came back

    dropped below minimum level
    poor local area circulation
    it was lurking

    try pouring some bleach in skimmer area, even a little inside skimmer and brush it (?)
    10000 Gal, IG Pebbletec, pop up cleaners,Hayward EcoStar VS, 425 sq ft Hayward Cartridge, waterfall feature

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    Mod Squad tim5055's Avatar
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    May 2014
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    Re: New Bloom of Algae, What am I doing wrong?

    Quote Originally Posted by Wildcat View Post
    In my opinion you are cutting your FC levels too close. If your CYA measurement is off, maybe it is 40, hardest measurement to do, you could be under FC levels needed.

    And why measure FC twice a day? Bring it up to max and let it drift down to mid point or minimum over a couple of days. While some will counter that you lose more at higher levels it is not that much and you are safer being at high end of range.

    Only three ways algae came back

    dropped below minimum level
    poor local area circulation
    it was lurking

    try pouring some bleach in skimmer area, even a little inside skimmer and brush it (?)
    I can agree that it is entirely possible that the FC is dropping too low, but at this point recommending only adding chlorine every couple of days is probably counterproductive. Many do it this way, even letting testing drop off to every 3 or 4 days, but that is AFTER the pool is clear and the owner has a good grasp of their pool and how it reacts.

    If there is visible algae then follow the SLAM Process all the way to the end. A good cleaning of the skimmer is in order if you see algae there.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: New Bloom of Algae, What am I doing wrong?

    Thanks for the reply Wildcat and Tim. The reason I do not think the FC dropped below 2 is that I test FC at least 2 x/day sometimes 4 depending on what is happening. I test FC before adding chlorine, so the lowest FC I ever had was 2.5, if it went lower it would have shown on testing. I know it is a lot of testing but between myself, wife and other family members we can do it. I test early in am before work and when I get home or before bed depending on if the solar cover was on or swimmers, etc. So if it got lower I would have known it unless there was error testing when it was low. The reason I have been testing so frequently because I know I have a low CYA (it is 30) is because I will be using Trichlor feeder when we go away for a week soon and that will take it up to 40 perhaps 50. Last year when I had it at 50 I bought a solar cover and using the solar cover, developed an algae bloom and it was more of a pain to SLAM at 50. I do believe 30 is correct my wife reads pretty close to the 30 line, I read as about half way between 20 and 30 which would then be read as 30 anyway. So if anything I think it may be a little under not over. I also bought a 50 reference so I would know more of what it was supposed to look like at a given level. Another reason I test frequently is I am using solar cover again and wanted to monitor closely. last year I did not take light out of niche, when I used cover got a bloom. this year I took out light and there was a lot of black algae in the niche, so I really inspected the pool found a very small bit of dried green behind the rubber ladder rest, cleaned that and scrubbed both returns very well when opening. But I will leave the possibility that there is someplace algae is was lurking as a reason for the bloom. Also the solar cover gets very dirty which ends up going in pool and in reading some old threads on solar covers it appears to be a moderately common problem but many use solar covers without any problems so I am thinking I am missing something just do not know what. I am also trying to stay pretty close to target # on charts for chlorine as it is fairly caustic and can decrease a solar covers life span (as well as bathing suits and other pool objects) if you go higher according to a post I read by chemgeek who I highly respect. so I am trying as best I can to keep the FC close to target level. Last year before I got solar cover I got so I could control FC testing 3-4 times a week and just adding a set amountof chlorine but this year with so many variables I wanted to keep as close an eye as possible so I know better what is happening. I want to update with a more automatic system such as a pump or SWG, just not really sure of which one and hate to spend all the money and then wish I went the other way, but summer is passing fast. The last area is circulation which may be a problem, especially with a solar cover. But I bought a robot this year and I run the pump 8 hours during the day and then usually 2 cycles of the cleaner at night which also shoots a lot of water around to increase circulation when pump not on. When I inherited this pool it did not have any eyeballs on the returns and I did not know I needed them but in researching this year I thought maybe that was a problem last year and put a venturi eyeball into deep end return and 3/4" on the shallow end return and have been playing around with them. When I add 1 it increases pump pressure about 3/4 lb and the second one increases pump pressure about 2 more lbs so I am not sure that is good for the system but it really causes a good counterclockwise rotation of the water and they were on when I discovered this new outbreak. So I am just looking for reasons so I do not continually go through this.
    28,000 gals (20 x 40), IG, vinyl, Hayward Sand Filter, old Hayward
    Super pump (not sure of HP secondary to corrosion of label),

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