Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 14 of 14

Thread: Black Algae and High CYA

  1. Back To Top    #1

    Black Algae and High CYA

    New member to the board . . . .any input/advise welcome.

    FC 1.0, CC 0, pH 7.8, Ca H 250, TA 80, CYA 120

    I have black algae starting on the steps and benches - first time for me. I have scrubbed the algae using a stainless steel brush and I just flushed the cartridges.

    I normally use the jumbo tabs with conditioner due to my travel/time-demands. I know that water replacement for high conditioner is the cost of this choice.

    I was going to shock the pool to eliminate the algae, but know that I need to drain the pool as well . . .. my question is - should I shock the pool first then drain the water, or drain the water, then shock? I know that I have to drain 1/2 to 2/3 of the water. Any other remedies or advice would be appreciated.

    Thanks
    20K Gal, Pebble, Sta-Rite VS-3050 (400-3450 rpm variable), Hayward C4020 400 sq ft cartridge filter, 1000 Gal Spa-spillover, Builit in 2001

  2. Back To Top    #2

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,085

    Re: Black Algae and High CYA

    Welcome to the forum. Drain first, refill and shock. You'll be able to give the black algae the old heave ho once you get it exposed.

    Pretty sure you know this but black algae seems to appear most frequently in pools that have been chronically underchlorinated. Not just days or weeks, but months.

    Keep that FC up probably at the very highest range of normal (actually, I would keep it 50% higher than that for a month or so) after you get refilled so it doesn't have a chance to get back....it's tough.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Black Algae and High CYA

    Don't forget to use a stiff brush (metal bristles are OK with a hard pool surface) to scrape off the waxy layer to expose the deeper layers of the algae to the high chlorine levels. With already established black algae, brushing is critical.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  4. Back To Top    #4
    y_not's Avatar
    Join Date
    Jul 2012
    Location
    Redmond, OR
    Posts
    1,086

    Re: Black Algae and High CYA

    Traveling a lot, you may be a good candidate for a SWCG unit and an acid pump.
    Thanks for reading... - Tony
    Da' Pool: Intex 15'x42" 3284gal AGP EasySet (Inflatable Ring) - (Summer 2014: 27' round EW /w 6.5' deep end @ 22,500gal)
    Pump & Cart Mod: 1000gph Cart. 5ft² - 2 nylons, 24/7 OP. Traps bugs/bits, lasts longer/cleans easier = Happier Pool Owner!!
    The Bible for a "Trouble Free Pool" life = PoolSchool, the BBB method a TF100 test kit(Recommend Kits Compared). - Cleaning a Sand Filter
    Water looks like GLASS, if yours doesn't...SLAM IT! Feels nice and never been happier!!! :D

  5. Back To Top    #5

    Re: Black Algae and High CYA

    Thank you very much for the help. I am assuming that the under-chlorination is due to the high CYA levels? I have pretty consistently had 1.5 readings for FC with no detectable CC. I had not been regularly testing for CYA.

    y_not - is there a thread on SWCG and acid pump that you would suggest? I would like to read-up on the subject as I am not really familiar with the equipment/costs/maintenance.

    Thanks again for the help.
    20K Gal, Pebble, Sta-Rite VS-3050 (400-3450 rpm variable), Hayward C4020 400 sq ft cartridge filter, 1000 Gal Spa-spillover, Builit in 2001

  6. Back To Top    #6

    Join Date
    Aug 2010
    Location
    Dallas, TX
    Posts
    4,052

    Re: Black Algae and High CYA

    1.0 FC, even 1.5, is WAY TOO LOW for that CYA. I would not recommend even trying to maintain a pool with little or no CYA at that level.

    How sure are you that your CYA is ONLY 120? CYA over 100 is very hard to measure and often the CYA is much higher than what the test reveals. Try mixing your pool water half/half with tap water and remeasure, then double the results.

    And I'm going to restate what was said above - WIRE BRUSH. If you don't break it up, you'll never defeat black algae.
    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
    If TFP has helped you, please click to SUPPORT TFP!

  7. Back To Top    #7
    y_not's Avatar
    Join Date
    Jul 2012
    Location
    Redmond, OR
    Posts
    1,086

    Re: Black Algae and High CYA

    Quote Originally Posted by ChrisMP
    y_not - is there a thread on SWCG and acid pump that you would suggest? I would like to read-up on the subject as I am not really familiar with the equipment/costs/maintenance.

    Thanks again for the help.
    No specific thread, not really. In this case the Google search box @ top is your friend. They go by many names, SWCG, SWG, salt water generator, salt water chlorine generator, salt pool, etc...
    Read about them in Pool School as well, see my sig or @ top right of any pg.
    If that doesn't do it for you, topic search can be found @ the extreme bottom left corner of the main TFP pg. It's an itty bitty, inconspicuous link. "advanced site search"

    Also, if you'd like, you can start a new thread under the SWG topic/forum to discuss SWCG options for your pool and needs.
    Normally we discourage from starting separate threads, however I would think it'd be OK as It's specifically pertaining to SWCG units, of which this this thread's topic has nothing to do with. Keep your CYA and current, non SWCG related water treatment problems to this thread, inline with its topic.
    But I'm not a mod, and It's ultimately up to them.
    Thanks for reading... - Tony
    Da' Pool: Intex 15'x42" 3284gal AGP EasySet (Inflatable Ring) - (Summer 2014: 27' round EW /w 6.5' deep end @ 22,500gal)
    Pump & Cart Mod: 1000gph Cart. 5ft² - 2 nylons, 24/7 OP. Traps bugs/bits, lasts longer/cleans easier = Happier Pool Owner!!
    The Bible for a "Trouble Free Pool" life = PoolSchool, the BBB method a TF100 test kit(Recommend Kits Compared). - Cleaning a Sand Filter
    Water looks like GLASS, if yours doesn't...SLAM IT! Feels nice and never been happier!!! :D

  8. Back To Top    #8
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: Black Algae and High CYA

    Welcome to TFP!!!

    I think you have not yet gained an understanding of the CYA/FC relationship as shown in the Pool School. Have you read it? Specifically : pool-school/chlorine_cya_chart_shock

    If your CYA was 100ppm, the MINIMUM that your FC must be to prevent any algae from starting to take hold is 7ppm ... obviously much higher than the 1.5ppm you reported. Your CYA is even higher, so your minimum FC level would be even higher.

    From that chart you should be able to realize that the tablets are just not a sustainable method of chlorination. They add FC and CYA. The FC is consumed, but the CYA builds up higher requiring more FC which adds more CYA:
    pool-school/types_chlorine_pool
    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
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  9. Back To Top    #9
    y_not's Avatar
    Join Date
    Jul 2012
    Location
    Redmond, OR
    Posts
    1,086

    Re: Black Algae and High CYA

    Quote Originally Posted by ChrisMP
    Thank you very much for the help. I am assuming that the under-chlorination is due to the high CYA levels? I have pretty consistently had 1.5 readings for FC with no detectable CC. I had not been regularly testing for CYA.
    As RobbieH said, that is nowhere near enough FC to keep algae at bay.
    FC shares a symbiotic relationship with CYA. As in, the higher your CYA, the higher your FC has to be for proper sanitation levels.

    For a CYA of 120ppm, you can't let your FC level drop below 8ppm at minimum, any given time of the day.
    See extended CYA chart in Pool School @ chlorine-cya-chart-t2346.html

    I would suggest you do some reading and studying in PS on how this all works.
    Thanks for reading... - Tony
    Da' Pool: Intex 15'x42" 3284gal AGP EasySet (Inflatable Ring) - (Summer 2014: 27' round EW /w 6.5' deep end @ 22,500gal)
    Pump & Cart Mod: 1000gph Cart. 5ft² - 2 nylons, 24/7 OP. Traps bugs/bits, lasts longer/cleans easier = Happier Pool Owner!!
    The Bible for a "Trouble Free Pool" life = PoolSchool, the BBB method a TF100 test kit(Recommend Kits Compared). - Cleaning a Sand Filter
    Water looks like GLASS, if yours doesn't...SLAM IT! Feels nice and never been happier!!! :D

  10. Back To Top    #10

    Re: Black Algae and High CYA

    Thanks for the help. I have started the drain on the pool and I have exposed the steps where the black algae was forming. I scrubbed it with a wire brush.

    I will start refilling and then shock the pool.

    I will definitely read up on the pool school materials (it's been a while) - especially the CYA-FC relationship

    And finally, I will see about getting off the tablets and going to liquid chlorine. I'll have to make some changes to how I manage the maintenance, but hopefully this can be avoided.
    20K Gal, Pebble, Sta-Rite VS-3050 (400-3450 rpm variable), Hayward C4020 400 sq ft cartridge filter, 1000 Gal Spa-spillover, Builit in 2001

  11. Back To Top    #11

    Join Date
    Aug 2010
    Location
    Dallas, TX
    Posts
    4,052

    Re: Black Algae and High CYA

    If you only travel occasionally, using tabs while you are gone is probably something that will work for you. But if you spend as much time away as me (50%+ travel, 4-5 days at a time), a SWG is something you should consider. With a 20k gallon pool, you might be able to get away with a Liquidator, but for me it did not have large enough capacity to maintain the pool while I was gone, and I still had to carry bleach bottles home.
    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
    If TFP has helped you, please click to SUPPORT TFP!

  12. Back To Top    #12
    y_not's Avatar
    Join Date
    Jul 2012
    Location
    Redmond, OR
    Posts
    1,086

    Re: Black Algae and High CYA

    Quote Originally Posted by RobbieH
    ...might be able to get away with a Liquidator, but for me it did not have a large enough capacity to maintain the pool while I was gone and I still had to carry bleach bottles home.
    Don't you have to carry acid bottles home too?
    Or is it simply the lesser of the 2?
    Thanks for reading... - Tony
    Da' Pool: Intex 15'x42" 3284gal AGP EasySet (Inflatable Ring) - (Summer 2014: 27' round EW /w 6.5' deep end @ 22,500gal)
    Pump & Cart Mod: 1000gph Cart. 5ft² - 2 nylons, 24/7 OP. Traps bugs/bits, lasts longer/cleans easier = Happier Pool Owner!!
    The Bible for a "Trouble Free Pool" life = PoolSchool, the BBB method a TF100 test kit(Recommend Kits Compared). - Cleaning a Sand Filter
    Water looks like GLASS, if yours doesn't...SLAM IT! Feels nice and never been happier!!! :D

  13. Back To Top    #13

    Join Date
    Aug 2010
    Location
    Dallas, TX
    Posts
    4,052

    Re: Black Algae and High CYA

    Yes, I deal with acid, but it isn't anywhere near my chlorine use. And if pH creeps up while I'm gone, my pool doesn't turn green.
    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
    If TFP has helped you, please click to SUPPORT TFP!

  14. Back To Top    #14
    y_not's Avatar
    Join Date
    Jul 2012
    Location
    Redmond, OR
    Posts
    1,086

    Re: Black Algae and High CYA

    *British voice*
    RIGHT, RIGHT, RIGHT.... GOOD SHOW! GOOD SHOW!
    Thanks for reading... - Tony
    Da' Pool: Intex 15'x42" 3284gal AGP EasySet (Inflatable Ring) - (Summer 2014: 27' round EW /w 6.5' deep end @ 22,500gal)
    Pump & Cart Mod: 1000gph Cart. 5ft² - 2 nylons, 24/7 OP. Traps bugs/bits, lasts longer/cleans easier = Happier Pool Owner!!
    The Bible for a "Trouble Free Pool" life = PoolSchool, the BBB method a TF100 test kit(Recommend Kits Compared). - Cleaning a Sand Filter
    Water looks like GLASS, if yours doesn't...SLAM IT! Feels nice and never been happier!!! :D

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •