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Thread: CYA level

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    CYA level

    Ok - I'm been reading info on your site to help with my recurrent green algae. I've come to the conclusion (for starters) that my CYA level continues to be too high because I am using trichlor tablets and shock. Do I understand correctly that I need to replace these chemcials with bleach? Does the pool calculator tell me how much to add and do I just pour it into the pool directly? Should I start here before making any other adjustments? Also, did I read that the only way to reduce CYA levels is to drain water?
    14,000 gallon in ground pebbletech pool
    Purex Clean & Clear Plus 2hp pump - Hayward Navigator

    Test Kit TF-100
    Cave Creek, Arizona

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    Join Date
    Feb 2008
    Location
    Denton, TX
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    Re: CYA level

    I'd be willing to bet that your CYA is, as you assume, a large contributor to the problem. But, in order for you to know for certain, you need to test your water with a reliable drop-based (no test strips please) test kit. Consider the TF-100 available at www.tftestkits.com or a Taylor K-2006.

    If you have been using stabilized chlorination products exclusively for a period of time, I have little doubt that your water is overstabilized. Stop using them now, test your water, post your results on this thread, and the experts here will help you get your water clear. While you are waiting for your test kit to arrive, take a water sample to a pool store and have them run a set of numbers for you. That will get you started.

    When using bleach, you are correct in assuming that you simply add it directly to the pool. Some pour it in a skimmer and this works great unless you have a skimmer sock over your basket. I learned that skimmer socks turn to mush after a couple of rounds of straight bleach. You can also pour it slowly in front of a return jet.

    As for lowering CYA, the only way that one can willfully lower it is by removing water (draining or splash-out).

    No worries. Fixing a green pool is pretty easy once you understand why they go green in the first place. What's better is that with BBB, you don't have to spend $$$$ at a pool store.

  3. Back To Top    #3

    Re: CYA level

    I tested my pool today (does have algae) and here are my results:
    FC-3 CC-0 TC-1 pH-7.7 T/A-110 CH-800 CYA-90

    I don't know if it matters, but the surface is pebbletech. Please let me know what to do first to begin the process of getting rid of the algae for good.

    Thank you!!!!!!
    14,000 gallon in ground pebbletech pool
    Purex Clean & Clear Plus 2hp pump - Hayward Navigator

    Test Kit TF-100
    Cave Creek, Arizona

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    TizMe's Avatar
    Join Date
    Aug 2007
    Location
    Covington, Georgia
    Posts
    920

    Re: CYA level

    Your TC can not be less than your FC are you sure of your TC number ? FC + CC = TC. Stop using the tabs and shock it will make your CYA rise thus making you use more chlorine to keep your algae under control.

    Refer to this chart to see what your minimum chlorine levels should be for your CYA. As you will notice the lower your CYA is the lower your min chlorine level is. Also in answer to your question the only way to lower your CYA level is to replace water. I read somewhere also that it will drop over the winter months so if you close it by draining it and covering it. Since its close to the end of the swim season you could wait util next season and adjust it when you open the pool back up.

    It would also be helpful if you added your pool type and equipment to your signature.
    Les
    Don't have a pool right now. Just sharing what I have learned over the years!
    Helpful Links:
    Pool School,Pool Calculator,Cl/CYA Shock Chart,TF Test Kit
    Doing BBB and loving it!

  5. Back To Top    #5

    Re: CYA level

    The TC should be 3 - I must have typed it wrong. As far as dropping the CYA, does the entire pool have to be drained or would half suffce? (I am in Arizona so we do not have to close our pools for the winter months.) So if I understand correctly, dropping the CYA level, changing to bleach and keeping all my other levels where they should be should solve my recurrent algae problem?

    Thanks so much for your quick replies!
    14,000 gallon in ground pebbletech pool
    Purex Clean & Clear Plus 2hp pump - Hayward Navigator

    Test Kit TF-100
    Cave Creek, Arizona

  6. Back To Top    #6
    JasonLion's Avatar
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    May 2007
    Location
    Silver Spring, MD
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    37,879

    Re: CYA level

    Replacing 40% of the water should do it. That will lower your CYA to between 50 and 55, which is a slightly high but very reasonable level. Once you have done that, you will be able to shock with FC around 17 and kill all the algae.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  7. Back To Top    #7

    Re: CYA level

    I want to make sure I understand so I don't screw it up! You said that after I drain about 40% of the water and refill, to shock the pool to bring my FC to 17. Does it sound right that I would add 377oz. of 6% bleach to accomplish that reading? How long do I need to run my pump after I brush all the algae and add the bleach? How long do I have to keep my FC at that level?

    Thanks!
    14,000 gallon in ground pebbletech pool
    Purex Clean & Clear Plus 2hp pump - Hayward Navigator

    Test Kit TF-100
    Cave Creek, Arizona

  8. Back To Top    #8
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: CYA level

    You should read this article on shocking and this article on fighting algae. Shocking requires testing and bringing FC back up to shock level over and over until all of the algae is dead.

    It takes 494 oz of 6% bleach to raise 14,000 gallons of water from a FC of zero to an FC of 17. If you have algae, your FC will be zero by now.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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