Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 11 of 11

Thread: Shocking and CC relationship -- question frrom newbie

  1. Back To Top    #1

    Join Date
    Apr 2013
    Location
    Phoenix AZ
    Posts
    20

    Shocking and CC relationship -- question frrom newbie

    I have finally decided to take control of my pool and have been reading the Pool School and these forums the past few weeks, but I do still have a question regarding the shocking process and how it affects combined chlorine. I *think* I understand the relationship but want clarification/confirmation.

    I understand that the TC = FC + CC. What exactly is combined chlorine? I originally thought that chlorine "combined" with the organics (e.g. algae) to produce CC but I don't think chemical compounds combine with organic material (I'm a few years out of school ) so that means the chlorine combines with other chemical compounds in the water to produce CC, but which what chemical? Shocking then oxidizes the CC into...what? How does adding more chlorine break down CC? And what is the result of that process, meaning does that produce other chemical compounds that have to be worried about?

    If these questions can't be answered without a chemistry explanation, just tell me "that's how it is, deal with it" and I'll understand
    ~20,000 gal in-ground plaster pool, 3/4 HP pump, ~3 sqft sand filter (newly replaced May 2013), TF-100 test kit with Speed Stir!

  2. Back To Top    #2
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: Shocking and CC relationship -- question frrom newbie

    Welcome to TFP!!!

    I am sure this is discussed in a thread somewhere ... although it is likely rampant with chemistry explanations.

    I don't understand the process myself, but the FC breaks down the organics and CC results, then the FC and sun break down the CC ... and then the pool is sparkly

    Maybe someone else will stop by with more info ... possibly more than you want to know.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  3. Back To Top    #3
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Shocking and CC relationship -- question frrom newbie

    First, one chlorine combines with any of various compounds containing nitrogen, typically organics like algae but also things like ammonia, to form CC, breaking down the original organic compound in the process. Then a second chlorine combines with the CC and breaks things down to more fundamental compounds, like water, salt, and nitrogen gas, that we don't worry about.

    If your FC level is reasonably high any CC created will be broken down fairly quickly and not enough will accumulate to create a measurable CC level. But if the FC level is quite low CC can be formed much more quickly than CC breaks down, leading to a measurable CC level.

    Much more detail about the chemistry is available in this post.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  4. Back To Top    #4

    Join Date
    Apr 2013
    Location
    Phoenix AZ
    Posts
    20

    Re: Shocking and CC relationship -- question frrom newbie

    Quote Originally Posted by JasonLion
    First, one chlorine combines with any of various compounds containing nitrogen, typically organics like algae but also things like ammonia, to form CC, breaking down the original organic compound in the process. Then a second chlorine combines with the CC and breaks things down to more fundamental compounds, like water, salt, and nitrogen gas, that we don't worry about.
    Gotcha. Basically it combines with "stuff" and becomes used up. This also means that CC isn't really an indicator that algae is present, right? Since it can combine with non-algae stuff like ammonia?

    Quote Originally Posted by JasonLion
    If your FC level is reasonably high any CC created will be broken down fairly quickly and not enough will accumulate to create a measurable CC level. But if the FC level is quite low CC can be formed much more quickly than CC breaks down, leading to a measurable CC level.
    I take it this is why people have said to shock the pool when CC gets too high. But what is "too high"? 1ppm? Is there an issue with having a high CC other than the smell and burning eyes I read about? Or is it that the OTO test kits become useless since CC skews the results (since they test TC)?

    Quote Originally Posted by JasonLion
    Much more detail about the chemistry is available in this post.
    "that's how it is, deal with it"
    ~20,000 gal in-ground plaster pool, 3/4 HP pump, ~3 sqft sand filter (newly replaced May 2013), TF-100 test kit with Speed Stir!

  5. Back To Top    #5

    Join Date
    Apr 2013
    Location
    Phoenix AZ
    Posts
    20

    Re: Shocking and CC relationship -- question frrom newbie

    Quote Originally Posted by jblizzle
    I don't understand the process myself, but the FC breaks down the organics and CC results, then the FC and sun break down the CC ... and then the pool is sparkly
    I'm sure this is all I really need to know, but sometimes my brain wants to know they "why" of it hehe
    ~20,000 gal in-ground plaster pool, 3/4 HP pump, ~3 sqft sand filter (newly replaced May 2013), TF-100 test kit with Speed Stir!

  6. Back To Top    #6
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: Shocking and CC relationship -- question frrom newbie

    Correct, CC does not necessarily mean algae ... ammonia will certainly show up as CC.

    CC > 0.5ppm indicate that something is going on in the water that should likely be taken care of through the shock process. It will contribute to the smell and irritation as well.

    We do not typically use the OTO for much. The test kits we recommend include the FAS-DPD chlorine test which is much more accurate and will test up to 50+ppm and give FC and CC individually.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  7. Back To Top    #7
    Mod Squad woodyp's Avatar
    Join Date
    Apr 2010
    Location
    East Texas
    Posts
    8,997

    Re: Shocking and CC relationship -- question frrom newbie

    A good hot sunshiney day will also burn off excess CC..........up to 1.5 anyhow that I know of.
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
    2 Speed Hayward Power-Flo Matrix 85 g.p.m. 22" 250lb. sand filter hard plumbed
    Pool Rover Jr., Pool Blaster Max, Diver Dave TF100 Test Kit/Speed Stir
    Margaritaville Frozen Concoction Maker, Liqour Chiller, & Drink Mixer & Party Tub----Collect 'um all!

  8. Back To Top    #8

    Join Date
    Apr 2013
    Location
    Phoenix AZ
    Posts
    20

    Re: Shocking and CC relationship -- question frrom newbie

    Quote Originally Posted by jblizzle
    We do not typically use the OTO for much. The test kits we recommend include the FAS-DPD chlorine test which is much more accurate and will test up to 50+ppm and give FC and CC individually.
    Ignore the signature, FedEx still has my TF-100, hehe.

    But, assuming a "negligible" CC of .5ppm, wouldn't an OTO test kit essentially report the FC level (I know it test TC) and use less expensive reagents to do so?
    ~20,000 gal in-ground plaster pool, 3/4 HP pump, ~3 sqft sand filter (newly replaced May 2013), TF-100 test kit with Speed Stir!

  9. Back To Top    #9

    Join Date
    Apr 2013
    Location
    Phoenix AZ
    Posts
    20

    Re: Shocking and CC relationship -- question frrom newbie

    Quote Originally Posted by woodyp
    A good hot sunshiney day will also burn off excess CC..........up to 1.5 anyhow that I know of.
    Oh, I thought UV burns the FC only. Good to know.
    ~20,000 gal in-ground plaster pool, 3/4 HP pump, ~3 sqft sand filter (newly replaced May 2013), TF-100 test kit with Speed Stir!

  10. Back To Top    #10
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Shocking and CC relationship -- question frrom newbie

    If CC is essentially zero, which it usually is, then the OTO test will report the FC level. However there are two problems, the first is minor, the second is major. First, you don't ever know for sure that CC is zero, so in rare cases the OTO test can fool you. Second, the OTO test is exceedingly difficult to read at FC levels above 2 or 2.5, or to put that another way, most people can't distinguish between the colors from an FC of 3 to FC of 10+, and that is the range we use the most.

    The OTO test is most useful as a quick chlorine/no chlorine test. Many people use it daily as a quick check that things haven't gotten completely out of hand, and get out a fancier test only once a week or when something is going wrong.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  11. Back To Top    #11

    Join Date
    Apr 2013
    Location
    Phoenix AZ
    Posts
    20

    Re: Shocking and CC relationship -- question frrom newbie

    Quote Originally Posted by JasonLion
    The OTO test is most useful as a quick chlorine/no chlorine test. Many people use it daily as a quick check that things haven't gotten completely out of hand, and get out a fancier test only once a week or when something is going wrong.
    This was essentially my plan once the TF-100 came in. But I have had the same issue with trying to match up the water color with the color chart. The water color was a "neon" yellow that didn't quite match with the chart. I figured that once I was reasonably sure CC was close to 0 I'd use the OTO to make sure there was chlorine in the water. As you said, if its difficult to read at FC above 2.5, as long as its above 2.5 I figured it should be good. Of course, I'm planning to use the TF-100 at least weekly once I can get into the swing of things (I expect I'll use it more often at first).
    ~20,000 gal in-ground plaster pool, 3/4 HP pump, ~3 sqft sand filter (newly replaced May 2013), TF-100 test kit with Speed Stir!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •