Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 5 of 5

Thread: Need some reassurance on CYA/FC relationship

  1. Back To Top    #1

    Join Date
    May 2016
    Location
    Fresno, CA
    Posts
    2

    Need some reassurance on CYA/FC relationship

    Okay, so I just test the CYA level of my parent's pool using the turbidity test. Results were 100ppm.

    I also tested the chlorine level using the Poolmaster OTO test and it is in the 2-3 ppm range.

    The pool looks good and it has been looking good for a while now.

    My question is: should I really add more chlorine because of the high CYA? Some of the charts I'm seeing about the chlorine/CYA relationship are telling me I should have about 7-10 ppm FC. I don't really have a huge problem doing that. I kinda of just want your feedback/experience, and I want to make sure it is safe, etc. It just seems really high to me...


    Pool is around 18,000 gal, in ground plaster with DE filter.

  2. Back To Top    #2
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: Need some reassurance on CYA/FC relationship

    Welcome to TFP!!!

    Following the FC/CYA chart is the only way to ensure the water is safe and will stay algae free and sanitized. It is safe.
    There is a chance your CYA is well above 100ppm and likely you should replace water.

    But, you need to get a better test kit ... see link in my Sig for the recommended test kit comparison shown in Pool School.
    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!

  3. Back To Top    #3

    Join Date
    May 2016
    Location
    Fresno, CA
    Posts
    2

    Re: Need some reassurance on CYA/FC relationship

    So assuming the 100ppm CYA reading is accurate, I should ditch the OTO for FAS/DPD and raise my FC to at least 7ppm?

    Also, some clarification would be great here. I though FC was the chlorine available to do work/sanitize, so wouldn't FC mean chlorine that is not bound up with CYA so 2-3ppm would be fine? I'm just a little confused, sorry.

  4. Back To Top    #4
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: Need some reassurance on CYA/FC relationship

    Yes, you need the FAS-DPD chlorine test.

    The FC is all the available chlorine including that which is bound to the CYA. If the FC is too low for your CYA level, most/all of it would be bound up with the CYA.

    Check this chart out (pay no attention to the colors, I am not sure what the green/blue are supposed to mean ):
    http://troublefreepool.com/~richardfalk/pool/HOCl.htm

    This shows the "active" chlorine level as a function of FC and CYA. If the HOCl is too low, the pool is not sanitized.
    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!

  5. Back To Top    #5

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,077

    Re: Need some reassurance on CYA/FC relationship

    changing the subject just a bit, you should NEVER trust the accuracy of the OTO chlorine test. That test will give you an indicator as to whether or not you have SOME chlorine but it is seldom accurate enough to tell you how much.

    Get yourself an FAS/DPD chlorine test and you won't have to guess.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

Posting Permissions

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