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Thread: Chlorine Drop from 4 to .5 while I was out of town

  1. Back To Top    #1

    Join Date
    May 2015
    Louisville, KY

    Chlorine Drop from 4 to .5 while I was out of town

    I thought you guys might find this interesting. I did.

    My pool is newly installed so I am still learning the ropes. However I have taken the advice of pool school here, so my water has been crystal clear. To be specific, here is where I keep my pool:

    CYA ~60
    FC ~ 3-4
    PH ~ 7.6
    CH ~200
    TA ~70
    Salinity ~3200

    I have a SWG and I have been running the pump about 12 hours a day, at about 25%, and checking my FC every few days. I was getting ready to go out of town for 4 days, so I set my intelliflow to run 6 hours a day, and set the SWG to 50% (suggested by someone here on this forum). I didn't know if this would be a good recipe for sure, but since I was going out of town, I figured it would be close enough.

    The day before I leave for town, we get the biggest rain of the year. The pool level was 1/2 way up the concrete coping! I had to dump about 1000 gallons out.

    Then I leave town.

    I come back to water that is... NOT crystal clear. It's not milky, but not clear either. I test the FC and it's about .5ppm, maybe less. Super low. So I start investigating, and here is what I think led to the problem.

    1. After all the rain, my salinity was 2700. So I guess the SWG was having a hard time making chlorine.

    2. The second day I was gone, my daughter came to use the pool at noon. The pump was off. At 1pm, the timer came on and the pump started running. She left at 2. She figured she should leave the pool as it was so she turned off the pump!

    3. The 4th day, I get home around 6pm and the pump isn't running. My wife had come home that day on her lunch, emptied the skimmer basket and jammed the floaty thing forward, so when the pump tried to kick on, it sucked air and never ran.


    I put the SWG into boost mode. The next morning the FC had not come up much at all. This is when I realized my salinity was only around 2700. I added a bag of salt and I put 1 gallon of bleach in, and left the SWG on boost mode for another 24 hours. After that, the FC was about 4ppm.

    Does it sound like the main problem was low salinity or the pump not running for 2 of the 4 days?
    Pool: 13,500 Gallon, San Juan StarDust Inground Fiberglass, installed May 2015
    Filter: Pentair cartridge filter, Clean and clear plus
    Main pump: Pentair Intelliflow | Booster pump: Pentair 3/4hp
    Pool Cleaner: Polaris 280 | Chlorine generator: AquaCal Autopilot Digital Nano Plus
    Filled pool with city water & using TF-100 test kit

  2. Back To Top    #2

    TFP Guide
    YippeeSkippy's Avatar
    Join Date
    Jan 2012
    'burbs of Augusta, Georgia

    Re: Chlorine Drop from 4 to .5 while I was out of town

    Could be all of the above in addition it seems to me that your FC level is being kept a bit low for your CYA
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