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Thread: Proper FC level for a SWG Pool

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    Join Date
    May 2013
    Egg Harbor Twp, NJ

    Proper FC level for a SWG Pool

    I've read throught the Pool School and many of the forums here with great interest and have learned an incredible amount. Here's my question though...according to the CYA/Chlorine chart, for a pool with a SWG and a CYA of 70, the FC level should be maintained at a target of 5 ppm (minimum of 3). However, according to my IC 40 SWG User Manual, it states FC of between 2.0 - 4.0, and specifically says "Above 4.0 ppm may cause corrosion of metal components". Is there any truth to this statement? Should I continue to maintain at 5.0 - 6.0 ppm as I have been or should I drop it down below 4.0?

    25,000 gallon IG gunite pool with Diamondbrite finish built May, 2012
    All Pentair equipment:
    FNS Plus 48 sq. ft. DE Filter, 1 HP SuperFlo Pump, IntelliChlor IC40 SWG, MasterTemp 400k BTU/HR Heater, Prowler 820 Vacuum
    Test Kit - TF-100

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Proper FC level for a SWG Pool

    You should use the number you find on the Chlorine/CYA chart. Most of the industry hasn't grasped the Chlorine/CYA relationship yet and base their numbers off faulty assumptions.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

  3. Back To Top    #3

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Proper FC level for a SWG Pool

    Quote Originally Posted by ssummer
    "Above 4.0 ppm may cause corrosion of metal components". Is there any truth to this statement?
    This would only be true if there were no Cyanuric Acid (CYA) in the water. As was noted by Dave, the industry doesn't understand the chlorine/CYA relationship. The active chlorine level at the minimum FC for SWG pools in the Chlorine / CYA chart is equivalent to only 0.05 ppm FC with no CYA. Even the shock FC level is equivalent to only 0.7 ppm FC with no CYA. Cyanuric Acid significantly moderates chlorine's active strength.
    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"

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