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Thread: What exactly happens to the Chlorine...

  1. Back To Top    #1

    Join Date
    Aug 2011
    Northville, Mi

    What exactly happens to the Chlorine...

    First - sorry if this has been answered (I didn't find it) or doesn't belong here...

    Being the geek that I am, I'm trying to make sense of exactly what goes on during the whole chlorine process and shocking.

    From the top...
    I put chlorine in the pool
    The chlorine finds "stuff" in the pool...sweat, microorganisms, whatever (?)
    The chlorine does something to the "stuff"...what? For some of it, it combines with it to become chloramines. These don't sanitize anything and cause that distinctive "chlorine" smell.
    Some of my chlorine gets broken down because of the sun. Where does it go?
    When I shock, all that extra free chlorine does what to the chloramines? And where does all that chlorine go?
    And, finally, and this may have been answered with the above questions, but, during normal operation, how does the chlorine get recycled so that my SWG doesn't eventually (and fairly quickly) just run out of NaCl to break down?

    Thanks for tolerating me.
    15,400 gal, 16x32 vinyl rectangle (sport dig), Intelliflo VS, 240 sqft cartridge filter, Intellichlor IC40, Mastertemp 250, Dolphin supreme M4 cleaning, Pentair EasyTouch4, Tested regularly and accurately with supplies from tftestkits

  2. Back To Top    #2

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: What exactly happens to the Chlorine...

    I believe this post has most of the answers you are looking for. During the day, most chlorine is usually broken down by sunlight to chloride salt. The chlorine that combines with ammonia to form monochloramine that registers as Combined Chlorine (CC) continues to get oxidized by chlorine to nitrogen gas and the chlorine becomes chloride salt (see this post for more technical details for chlorine oxidation of ammonia and this post for some speculation on chlorine oxidation of urea but where the chloramines get further oxidized as with the ammonia model). With an SWG system, the chloride salt gets converted back to chlorine (hypochlorous acid or more accurately hypochlorite ion after combining with the hydroxyl ions from the other plate). So with an SWG, the chlorine is recycled except for a small amount of hypochlorous acid that outgasses and a small amount of combined chlorine that gets filtered out and the amount of chlorine and chloride salt that get diluted by splash-out, carry-out, backwashing, etc.
    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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