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Thread: Black spots - algae?

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    poollizard's Avatar
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    Black spots - algae?

    I'm getting ready to drain and refill my pool in order to reduce the CYA and CH. I also have three black spot areas that I can't brush out, I was wondering how to remove the spots after all the water is drained.

    Here are my test results from yesterday:

    FC = 8
    CC = .5
    pH = 7.5
    TA = 150
    CH = 600
    CYA = 240
    21,500 Gal IG plaster, free form, PAC-FAB NAUTILUS NFS-60 DE filter; Pentair Intelliflo VF pump; TELEDYNE LAARS Series One gas heater. Hayward PoolVac V-Flex pool cleaner. Taylor K-2006 test kit.

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    Re: Black spots - algae?

    My guess is black algae, can you post a picture. Removal of black algae is difficult. I use a wire brush. You should be able to scrape some off with a fingernail or knife, then squish it to see if it turns a dark green to ensure it is black algae. If you are draining, I would scrub with a wire brush then spray with a water/bleach solution.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    poollizard's Avatar
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    Re: Black spots - algae?

    I do have a picture of one of the spots. This was taken this morning, through the water. It's not a very good picture. I also have a lot of scale. The other blotches are clear places in the scale.


    21,500 Gal IG plaster, free form, PAC-FAB NAUTILUS NFS-60 DE filter; Pentair Intelliflo VF pump; TELEDYNE LAARS Series One gas heater. Hayward PoolVac V-Flex pool cleaner. Taylor K-2006 test kit.

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    poollizard's Avatar
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    Re: Black spots - algae?

    I'm getting ready to pump, any advice?
    21,500 Gal IG plaster, free form, PAC-FAB NAUTILUS NFS-60 DE filter; Pentair Intelliflo VF pump; TELEDYNE LAARS Series One gas heater. Hayward PoolVac V-Flex pool cleaner. Taylor K-2006 test kit.

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    Re: Black spots - algae?

    Looks like black algae. Wire brush. A small one will be more effective.

    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    poollizard's Avatar
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    Re: Black spots - algae?

    See the white blotches? What is that? Is that calcium scale buildup? They feel smooth to the touch.




    21,500 Gal IG plaster, free form, PAC-FAB NAUTILUS NFS-60 DE filter; Pentair Intelliflo VF pump; TELEDYNE LAARS Series One gas heater. Hayward PoolVac V-Flex pool cleaner. Taylor K-2006 test kit.

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    Re: Black spots - algae?

    It could be. I'll let someone with experience with scaling give you advise.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    poollizard's Avatar
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    Re: Black spots - algae?

    The more I look at it, the more I think it is the paint coming off. I can remember this whitish look getting worse and worse over the last 5 to 9 years. It could be scale I suppose, but when I run my finger over it the whitish ares are smooth, and then the other areas are kind of rough, like a pool bottom is supposed to be. There are no cracks or chipping any where on the surface. I am really beginning to think it's just that the paint has come off.

    Any other opinions?
    21,500 Gal IG plaster, free form, PAC-FAB NAUTILUS NFS-60 DE filter; Pentair Intelliflo VF pump; TELEDYNE LAARS Series One gas heater. Hayward PoolVac V-Flex pool cleaner. Taylor K-2006 test kit.

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    Re: Black spots - algae?

    After refilling my pool, can I use the SLAM method to get it rebalanced? Or is there another recommended procedure?


    Oh yea, what is "shock level", referred to in the SLAMing procedure.
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    21,500 Gal IG plaster, free form, PAC-FAB NAUTILUS NFS-60 DE filter; Pentair Intelliflo VF pump; TELEDYNE LAARS Series One gas heater. Hayward PoolVac V-Flex pool cleaner. Taylor K-2006 test kit.

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    Re: Black spots - algae?

    Was the pool painted?

    Calcium scale usually feels rough. But if the pool had white plaster, some of the smooth areas could be places that don't have scale. I can't tell from the pictures.


    Once you refill, you can adjust your water balance to prepare for a SLAM and then start it. Did you validate that you have black algae?


    Edited to add: Chlorine level for the SLAM can be found here: pool-school/chlorine_cya_chart_shock.
    Outdoor 14,000 gallon IG plaster pool built in 2000 with spillover spa, 2 hp WhisperFlo pump with MagneTek motor, Sta-Rite cartridge pool filter with 300 ft2 filtration area and 0.33 gpm/ft2 filtration rate, Aquabot Rapids 4WD robotic pool cleaner, Raypak digital gas heater, and Intermatic mechanical timer located in the Dallas-Fort Worth metroplex

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    Re: Black spots - algae?

    "Shock Level" is an increase from the normal level of FC that is designed to effectively kill any organics in your water while minimizing the risk of damage to your pool or plumbing. During the SLAM process FC is raised to shock level and maintained as closely as possible until you can pass an Overnight Chlorine Loss Test. Afterwards, the higher level is allowed to drop back into the normal maintenance range.
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    Relative's IG Vinyl | 16x32 | ~18,600 gals | Hayward 3/4hp Pump | Hayward S244T Filter | Pentair Model 300 Chlorinator (not used) | Polaris 180

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    Re: Black spots - algae?

    Quote Originally Posted by danacc
    Was the pool painted?

    I don't have any details of the original construction of the pool. But I do believe it was painted.

    Calcium scale usually feels rough. But if the pool had white plaster, some of the smooth areas could be places that don't have scale. I can't tell from the pictures.

    In those areas where the paint is gone it feels smooth, and the color is either white or light gray.


    Once you refill, you can adjust your water balance to prepare for a SLAM and then start it. Did you validate that you have black algae?

    Do you mean to follow the SLAMing procedure after the refill?

    I believe it is black algae. I need to finish draining in the morning and then attack the black algae.


    Edited to add: Chlorine level for the SLAM can be found here: pool-school/chlorine_cya_chart_shock.
    Thank you!!!
    21,500 Gal IG plaster, free form, PAC-FAB NAUTILUS NFS-60 DE filter; Pentair Intelliflo VF pump; TELEDYNE LAARS Series One gas heater. Hayward PoolVac V-Flex pool cleaner. Taylor K-2006 test kit.

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    Re: Black spots - algae?

    Quote Originally Posted by Jeetyet
    "Shock Level" is an increase from the normal level of FC that is designed to effectively kill any organics in your water while minimizing the risk of damage to your pool or plumbing. During the SLAM process FC is raised to shock level and maintained as closely as possible until you can pass an Overnight Chlorine Loss Test. Afterwards, the higher level is allowed to drop back into the normal maintenance range.

    Thank you for the explanation.
    21,500 Gal IG plaster, free form, PAC-FAB NAUTILUS NFS-60 DE filter; Pentair Intelliflo VF pump; TELEDYNE LAARS Series One gas heater. Hayward PoolVac V-Flex pool cleaner. Taylor K-2006 test kit.

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    Re: Black spots - algae?

    Well, I got the black algae off, refill in progress.

    It's obvious to me now that the pool surface needs repainting. I am going to tackle that job later this year or in the spring. Sometime when the weather is more suitable. Right now we are still having 100 degree temps. Ugh!!
    21,500 Gal IG plaster, free form, PAC-FAB NAUTILUS NFS-60 DE filter; Pentair Intelliflo VF pump; TELEDYNE LAARS Series One gas heater. Hayward PoolVac V-Flex pool cleaner. Taylor K-2006 test kit.

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