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Thread: How to kill Black Algae

  1. Back To Top    #1

    Join Date
    Jun 2008
    Location
    Texas
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    132

    How to kill Black Algae

    I have two related problems. First my pool needs to be replastered. Second black algae started this winter. The black spots disappear after treatment with trichlor. The poor condition of the white plaster may have allowed the algae a place to start. Our pool is about 23 years old and I believe that the pool has never been replastered.

    Late in the fall I noticed a rust stain in the shallow end of our pool. I had no idea what was wrong since I had never knew that a pool owner needs to replaster their pool. Since I started on the BBB method 6 years ago I have never had any algae. My SWG does not produce Cl in the winter so the FC was 0 during the winter. In previous years I monitored the FC as soon as the pool temperature reached 60 degrees. I was prepared to brush the algae with a metal brush and attack the black algae with a SLAM, copper algaecide, granulated trichlor and rubbing trichlor tablets on the black algae.

    I now wonder if I should wait and attack the black algae after the pool has been drained. I could then pressure wash the pool, wash with a chlorine bath, and/or an acid bath. Since this will be the best opportunity to get rid of all black algae spores I want to hit the black algae hard now and not have to fight black algae for ever and ever. I might choose a colored plaster so Cl staining could be an issue in the future.

    I currently am gathering bids to replaster the pool with Diamond Brite. I live in a rural area so I may have to contract with a plastering company over 100 miles distant. I plan to drain the pool and attack the black algae before the plastering begins. I want to have the pool replastered as soon as I can select a plastering company.

    Questions:
    1. To drain the pool should I use sump pump and the main pool pump?
    2. What psi should I use to pressure wash? Should I use a broad tip or a narrow tip?
    3. Should I start killing the black algae now or wait until the pool is drained?
    4. When the pool is drained I will want to minimize the time the pool is drained. Would I be able to spot the black algae, brush it and kill it with bleach in one day?
    5. What concentration of bleach should I use? e.g. 1:1? Should I use a pump sprayer or a sprinkling can?
    6. Should I use the copper algaecide and granulated trichlor when the pool is drained?
    7. Is there any reason to acid wash the pool?
    8. How long does the pool need to dry before the plaster can be applied?
    9. I have a sand filter using zeobrite. How should I sanitize my filter?
    10. I have rusted rebar. How should this be fixed?
    11. I plan to replace the hydrostatic valves. Do you recommend any other upgrades I should do at this time.
    12. Any advise on how select and contract with a plastering company located in another city.
    Attached Images Attached Images
    30,000 gallon gunite in-ground with a spillover spa, Diving board and water slide
    Hayward 1 HP Super II filter pump, Hayward 24 " Sand Filter Pro Series using zeolite media
    Polaris 380 cleaner with ¾ HP booster pump, Hayward Heatmaster pool heater, AutoPilot DIG-220 Power Supply SC-60 cell
    Testing with the TF-100 Test Kit

  2. Back To Top    #2
    Mod Squad kimkats's Avatar
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    Jul 2012
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    Tallahassee, FL
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    Re: How to kill Black Algae

    I think these would all be good questions to ask your new plaster people. They are the ones that do this kind of thing for a living.

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

  3. Back To Top    #3
    Mod Squad jblizzle's Avatar
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    Re: How to kill Black Algae

    If you are draining the pool to get it re-plastered, there is no reason to worry about the algae. They should chip out all the old plaster down to the structure, thus removing all the algae, and then apply the new plaster to the roughed up sub-surface.

    Also, the plaster company will be the ones draining the pool, so I would not worry about it. They will also chip out around the rusting re-bar and recover that with concrete before the re-plaster.

    Post back if I am overlooking something.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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  4. Back To Top    #4

    Join Date
    Jun 2008
    Location
    Texas
    Posts
    132

    Re: How to kill Black Algae

    I am concerned to rely on local pool companies without more knowledge. If I lived in an area like south Florida with many reputable pool companies I might just follow their advise without question. After we purchased our house I discovered that the pool electrical equipment was wired with bare wires running across a wet equipment room floor. The Polaris pump was wired to run without the main pump running. I placed the wires in conduit stapled to the walls and required the Polaris to run only when the main pump is running. A pool tech told me that he only worked for the pool company when he was laid off from his real job! After I started testing with the TF-100 Test Kit I balanced my water to perfection. I went to a pool store to purchase muriatic acid and told them that my water was crystal clear. They recommended over $130 worth of chemicals including clarifiers, algaecides, and phosphate removers. I have not found a single local pool technician that has had training by a manufacturer. I know that not every recommendation made by a pool store is in my best interests.

    Since the replastering companies may be a two plus hour drive distant I thought that I might have to drain the pool on day one and have their team arrive on a subsequent day.

    I do not see any plaster delamination or plaster spalling. JasonLion in the below link discusses that there are pools that may require only sandblasting.

    Pool replaster question? out old plaster

    I do not want to require a chip out to get rid of black algae if all the surface requires is a sandblasting.

    I have read that black algae can grow roots into the gunite. If this is true the algae could reemerge through a new plaster job.
    30,000 gallon gunite in-ground with a spillover spa, Diving board and water slide
    Hayward 1 HP Super II filter pump, Hayward 24 " Sand Filter Pro Series using zeolite media
    Polaris 380 cleaner with ¾ HP booster pump, Hayward Heatmaster pool heater, AutoPilot DIG-220 Power Supply SC-60 cell
    Testing with the TF-100 Test Kit

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