Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 7 of 7

Thread: Free Chlorine loss vs UV index

  1. Back To Top    #1

    Join Date
    Jul 2013
    Location
    Spring, Tx
    Posts
    49

    Free Chlorine loss vs UV index

    has anyone investigated the relationship of FC loss to the UV index?

    I was calculating the balance point for my SWG based on 60% loss due to UV and I wondered if the relationship is linear to the UV index.

    My pool should be stable at 5ppm with the cell set to 63% with a 10 hour pump time if the 60% loss holds true.
    ~16.5Kgal free form plaster with spill over spa
    1 1/2 HP Pentair SuperFlo pump, 1 HP Polaris QT Spa Blower, Pentair 48sqft DE Filter, PoolPilot Digital Nano+ SWG

  2. Back To Top    #2
    linen's Avatar
    Join Date
    Jul 2010
    Location
    Twin Cities, MN
    Posts
    8,649

    Re: Free Chlorine loss vs UV index

    I am not sure if that correlation has been studied. 60% loss is really high though. What cya level are you maintaining?
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  3. Back To Top    #3

    Join Date
    Jul 2013
    Location
    Spring, Tx
    Posts
    49

    Re: Free Chlorine loss vs UV index

    It was 45 yesterday. I added a gallon of liquid CYA this afternoon. I just finished SLAMming this morning. I didn't want to crank the CYA up until after I had finished. It's possible that my loss will drop now that I'm not feeding my FC to organics.
    ~16.5Kgal free form plaster with spill over spa
    1 1/2 HP Pentair SuperFlo pump, 1 HP Polaris QT Spa Blower, Pentair 48sqft DE Filter, PoolPilot Digital Nano+ SWG

  4. Back To Top    #4

    Join Date
    Jul 2013
    Location
    Spring, Tx
    Posts
    49

    Re: Free Chlorine loss vs UV index

    UV index today was 11 (Extreme)
    ~16.5Kgal free form plaster with spill over spa
    1 1/2 HP Pentair SuperFlo pump, 1 HP Polaris QT Spa Blower, Pentair 48sqft DE Filter, PoolPilot Digital Nano+ SWG

  5. Back To Top    #5
    linen's Avatar
    Join Date
    Jul 2010
    Location
    Twin Cities, MN
    Posts
    8,649

    Re: Free Chlorine loss vs UV index

    With cya up in our recommended range of 70-80 ppm (and no organics), you should see much less loss (I see about 10-20%/day).
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  6. Back To Top    #6

    Join Date
    Jul 2013
    Location
    Spring, Tx
    Posts
    49

    Re: Free Chlorine loss vs UV index

    With the CYA I added this afternoon I should be ~60. I'll confirm tomorrow and add another gallon. I'm adding slowly because I really don't want to overshoot.
    ~16.5Kgal free form plaster with spill over spa
    1 1/2 HP Pentair SuperFlo pump, 1 HP Polaris QT Spa Blower, Pentair 48sqft DE Filter, PoolPilot Digital Nano+ SWG

  7. Back To Top    #7

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Free Chlorine loss vs UV index

    The UV Index calculation is described in this EPA link where you can see that the amount of UV radiation by wavelength is weighted by its effects on human skin. The UV index is overweighted at 400 nm compared to chlorine loss since the molar extinction coefficient is low at that wavelength. Their 320 nm peak is similar to that for chlorine but they assume more UV gets through at 290 nm than is actually the case according to standard sun irradiance.

    At any rate, the UV index would be a reasonable number to use to assess predicted chlorine loss from the UV in sunlight -- not perfect, but not horrible either.
    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
  •