Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 4 of 4

Thread: Question about CYA and FCC relationship.

  1. Back To Top    #1

    Join Date
    Jul 2015
    Lake Elsinore, CA

    Question about CYA and FCC relationship.

    How come chlorine / other pool care productions don't mention the CYA FCC relationship? Where can I go to learn more about this relationship?

    Pool a supply stores never mentioned this either?
    Intex 9 x 15 x 52" 5000 gal, vinyl, Sand filter pump, Taylor K-2006

  2. Back To Top    #2

    TFP Guide
    pabeader's Avatar
    Join Date
    May 2015
    Dallas Ga

    Re: Question about CYA and FCC relationship.

    Because if they admit it, they would be out of business.

    You can start here:
    Bob - Palm Beach by San Juan Pools. approx 5000 gals Pentair 320 cartridge filter (all new guts installed by me) Goldline SWG Intermec 104 TImer Test kit K-2006-C

  3. Back To Top    #3
    Mod Squad Patrick_B's Avatar
    Join Date
    Jun 2011

    Re: Question about CYA and FCC relationship.

    Many are also unaware, and the FC CYA relationship is just plain misunderstood by many others. Unfortunately, the government, and most industry "authorities" don't recognize it.
    TFP Moderator
    Essential Links:
    TF-100 Test Kit, ABC's Of Pool Chemistry, Test Kits, SLAM Your Pool
    28K Gal IG FreeForm, CLI Quartz, Flagstone, 36"SF, Pentair VS Pump, EasyTouch W/Remote, Rheem 400KBTU Htr

  4. Back To Top    #4

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Question about CYA and FCC relationship.

    It's a chemical fact known since at least 1974 as defined definitively by the equilibrium constants determined in this paper. It was known even before then, but all of the equilibrium constants had not been worked out. The bottom line is that the active chlorine (hypochlorous acid) level that determines the rate of disinfection, killing of algae, and oxidation of bather waste is proportional to the FC/CYA ratio (when CYA is present). So if the CYA rises over time and you don't proportionally raise the FC, then the ratio drops which means that in the presence of sufficient nutrients algae can grow faster than chlorine can kill it.

    It's not just the FC/CYA relationship that the pool/spa industry chooses to ignore, but also the following chemical facts that are independent of concentration of product or of pool size:

    For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
    For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
    For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.
    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"

Posting Permissions

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