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

Thread: Does chlorine really get used up that fast?

  1. Back To Top    #1
    surfhawaii's Avatar
    Join Date
    May 2011
    Location
    Kailua, Hawaii
    Posts
    61

    Does chlorine really get used up that fast?

    FC in the morning was 7, twelve hours later it's at 0. Now, CYA level is still at zero because I just added it a few days ago and it's slowly dissolving thru socks and I think you said it takes a week or so to register so maybe it's not helping to keep chlorine in the water (and it was a fairly sunny day), but can it drop that much in 12 hours?
    24.5k gallon
    Sand filter (Triton II TR 100)
    IG tile
    Pentair VS+SVRS pump
    Sundance Chelsee spa

  2. Back To Top    #2

    Join Date
    Feb 2008
    Location
    Denton, TX
    Posts
    5,061

    Re: Does chlorine really get used up that fast?

    It can drop that much in a couple of hours. CYA is that important.

  3. Back To Top    #3
    frustratedpoolmom's Avatar
    Join Date
    May 2007
    Location
    SWSuburban Chicago, IL
    Posts
    11,965

    Re: Does chlorine really get used up that fast?

    While it takes a week to fully register on tests - it should start to work within the first 24-48 hours. I'm guessing there is something lurking consuming the chlorine as well. The best way to rule out sunlight is to dose the chlorine in the evening when the sun is off the pool and see what kind of overnight drop you have. If it drops more than 1ppm then it's not from the sun. KWIM?
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

  4. Back To Top    #4
    dmanb2b's Avatar
    Join Date
    Apr 2009
    Location
    NY
    Posts
    3,728

    Re: Does chlorine really get used up that fast?

    Like FPM, you may have a combo of still too low CYA and possible organics...as she suggested the overnight FC loss test would be your best bet. Here is a link to the instructions

    pool-school/overnight_fc_test
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

    Pool School, TFTestKits, Pool Calculator

  5. Back To Top    #5
    surfhawaii's Avatar
    Join Date
    May 2011
    Location
    Kailua, Hawaii
    Posts
    61

    Re: Does chlorine really get used up that fast?

    Ok. Will do. Also, got a few more questions:

    Yesterday I cut the grass and weedwhacked around the pool perimeter. Even though I use a grass catcher and try to blow grass away from the pool, the trade winds blow grass trimmings into pool and there is no way from preventing almost the entire surface of the pool from being lightly covered with grass. I try to skim off as much as I can but know I don't get it all. Could this be contributing or no big deal?

    Is combined chlorine an issue, should I be measuring/tracking? I don't see much reference to it. It's been zero.

    I see lots of references in pool school to shocking. And understand that could be bleach but when you say 'shock' it and/or 'continue shocking', what exactly does that mean with regard to how much to add? Or is there a better chemical to use?

    As always, thanks for your prompt responses.
    24.5k gallon
    Sand filter (Triton II TR 100)
    IG tile
    Pentair VS+SVRS pump
    Sundance Chelsee spa

  6. Back To Top    #6
    frustratedpoolmom's Avatar
    Join Date
    May 2007
    Location
    SWSuburban Chicago, IL
    Posts
    11,965

    Re: Does chlorine really get used up that fast?

    Bleach a.k.a. liquid chlorine is the preferred product for shocking. In some cases, dichlor granules or cal-hypo granules can be used to shock.

    Use the Pool Calculator to figure out amounts of each chem to add - if you need help on learning to use it, just holler.

    Combined Chloramines, CC's are important in that if they get above .5 you usually should shock the pool. Sometimes sunlight helps rid the pool of them but if they get much higher than .5 that's a sign something organic is happening.

    I wouldn't worry about the grass.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

  7. Back To Top    #7

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

    Re: Does chlorine really get used up that fast?

    Quote Originally Posted by surfhawaii
    FC in the morning was 7, twelve hours later it's at 0.
    If there is no CYA in the water, then at a pH of 7.5 chlorine in an average depth pool will drop in half every hour in direct noontime sun. 12 hours is roughly equivalent to around 8 or so hours of direct noontime sunlight so 7 ppm FC would get to 7*(0.5)8 = 0.03 ppm which would register as zero on a test kit. Even after 4 hours near noontime, it would go from 7 ppm FC to around 0.4 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
  •