Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 12 of 12

Thread: Is 10ppm FC safe to swim in?

  1. Back To Top    #1
    Guest

    Is 10ppm FC safe to swim in?

    I remember hearing that generally Free Chlorine levels can be much higher than the pool stores will recommend.

    I was having a problem getting my FC to hold. Last night, I finally decided to do a good shocking. I used 3 gallons of 10% bleach.
    By morning my FC was holding at 11ppm. Later that day my wife had a friend and her two young boys, aged 4 and 2 over and they swam for about a half hour.
    When I got home, I checked the FC and it was still 9.5 and that was after a good rain shower. I figured the boys must have been swimming in 10PPM FC before it rained.

    The good news is that the free chlorine is holding. Is there any health risks swimming in it or getting a mouthful of 10ppm chlorinated water?

  2. Back To Top    #2

    Join Date
    May 2009
    Location
    Jasper, TN
    Posts
    249

    Re: Is 10ppm FC safe to swim in?

    Just from general info I have gotten from this site so far, my uneducated guess is no as 10ppm is not shock level. Though it will likely be a little irritating to the eyes.

    Someone more knowledgeable will chime in to verify I'm sure.

    The main reason I wanted to reply is where do you get 10% bleach?
    24' x 52" AGP = 13.5k gallons
    Dynamo 2.0 HP pump,Sand Dollar sand filter
    Polaris 65 vacuum (good when there are a ton of leaves on bottom), Pool Rover Jr. (LOVE it, but power box dead right now), AquaCritter (an excellent suction side cleaner)

  3. Back To Top    #3

    Join Date
    Jun 2009
    Location
    Riverside, CA
    Posts
    62

    Re: Is 10ppm FC safe to swim in?

    I saw your question and in CA we get our 10% as chlorine at Lowe's. I can't find 12.5% here and was wondering where everyone on the forum gets that.

    rbdeli, I've had the same question about swimming at FC 10 and haven't gotten an answer yet. Hopefully we will get an answer to that question. I can't get my FC to hold overnight, but would like to swim during the day when the levels go down. I don't have CYA in my pool yet.
    10,000 gallons Splash Pool; cartridge filter; vinyl; AG; pump Sta-Rite 1 HP

  4. Back To Top    #4
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Is 10ppm FC safe to swim in?

    How safe high FC levels are depends on your CYA level. I will swim from the minimum FC level to the shock FC level on the Chlorine/CYA chart. If you don't have any CYA in the pool, then a FC of 10 is too high. But more or less as soon as you have some CYA in the pool, an FC of 10 is fine.
    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

  5. Back To Top    #5

    Join Date
    Jul 2008
    Location
    Clovis,Ca
    Posts
    54

    Re: Is 10ppm FC safe to swim in?

    Quote Originally Posted by horsegal
    I saw your question and in CA we get our 10% as chlorine at Lowe's. I can't find 12.5% here and was wondering where everyone on the forum gets that.
    Try a pool store near you. Our local Leslies carries it, but it is big $$.

    I found a mom and pop pool store that has it, $13.99 for 4 gals.!!!!

    C-Ya!!

  6. Back To Top    #6
    Guest

    Re: Is 10ppm FC safe to swim in?

    K-Mart, of all places, is where I get 10% bleach. However, Walmart's great value bleach in the big jugs is now a little less money!

  7. Back To Top    #7

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

    Re: Is 10ppm FC safe to swim in?

    I responded to similar questions of high FC safety on other forums so the question comes up a lot. As far as harshness on the eyes, it is only the active chlorine (hypochlorous acid) that is the strong oxidizer that would affect the eyes so you can't look at FC alone. Also, pH is a much bigger factor than chlorine level in terms of eye irritation unless the active chlorine level gets very high (i.e. no CYA such as in indoor pools and an FC that is higher).

    The EPA limit for chlorine is 4 ppm FC, but this is based on drinking water (6-8 quarts per day every day) and does not take into account skin absorption nor the fact that most of the chlorine is not active (hypochlorous acid) but is instead bound to Cyanuric Acid (CYA) in chlorinated cyanurates as described in the technical paper in this link. The manufacturers of chlorine products are required to follow FIFRA guidelines for labels and unfortunately this includes this EPA limit. I've contacted the EPA and found that the group that manages disinfectants (including that for use in swimming pools) was not even aware of the chlorine/CYA relationship (even though it was indirectly implied in section 7a of this EPA PDF file).

    There is not any skin absorption data for the chlorinated cyanurates themselves, but as noted in this PDF file, skin absorption of CYA is minimal (5 µg/kg/day) and it's likely that the same is true for the chlorinated cyanurates (i.e. chlorine bound to CYA), especially since the primary species are negatively charged.

    With the FC kept at around 10% of the CYA level, the active chlorine (hypochlorous acid concentration) is roughly the same as in a pool with 0.1 ppm FC and no CYA.

    There are quite a few pool services in desert regions that raise the FC to 14 ppm with 100 ppm CYA which then drops to around an FC of 4 ppm the following week when they add more chlorine again. People don't even notice these high FC levels since the reaction rates and outgassing of chlorine are all determined by the active chlorine concentration and not the FC level. FC alone is really a chlorine capacity or the amount in reserve and is not an indication of chlorine "activity" or power in the water.

    My wife swims in an indoor community center pool over the winter that has 1-2 ppm FC with no CYA and she has to replace her swimsuits after just one winter season of use because the elasticity wears out. Also, her skin gets flaky and hair frizzy so she uses chlorine neutralizing shampoo and soap. None of these problems occur in our own outdoor pool during a longer 7-month summer swim season where our pool has 3-4 ppm FC with 30 ppm CYA. Swimsuits have lasted for years with minimal degradation and her skin and hair aren't as negatively affected. I believe that the difference in her experience is the 10-20 times lower active chlorine concentration in our pool. There are also implications to the rate of production of disinfection by-products in a pool without CYA, but I won't get into that here.

    Richard
    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"

  8. Back To Top    #8

    Join Date
    Jun 2009
    Location
    Riverside, CA
    Posts
    62

    Re: Is 10ppm FC safe to swim in?

    chemgeek,
    Thanks for that detailed explanation. I got a degree in biology and took a fair amount of chemistry in college, but pool chemistry still baffles me at times. If I am understanding you correctly, it depends upon your CYA level as to what a safe FC swimming level truly is. I always thought that the degraded elasticity in swimsuits in indoor pools was more related to chloramine levels. Indoor pools always seem to have that "smell" that I thought was actually caused by chloramines, not free chlorine. horsegal
    10,000 gallons Splash Pool; cartridge filter; vinyl; AG; pump Sta-Rite 1 HP

  9. Back To Top    #9
    frustratedpoolmom's Avatar
    Join Date
    May 2007
    Location
    SWSuburban Chicago, IL
    Posts
    11,965

    Re: Is 10ppm FC safe to swim in?

    The smell in indoor pools is usually attributed to poor ventilation and chloramines. The degredation is a result of the high FC ratio.
    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

  10. Back To Top    #10
    Guest

    Re: Is 10ppm FC safe to swim in?

    I have recent experience on that count.

    My wife and I stayed at a Hotel in southern Kansas a week ago. It had an atrium with indoor pool. The whole atrium smelled like mold. The pool was green and nearly impossible to see the bottom. Knowing what a nut I've become on testing our own pool, my wife was furious that I didn't bring a pool testing kit with me. She actually was curious what we might find out.

  11. Back To Top    #11
    Guest

    Re: Is 10ppm FC safe to swim in?

    Thanks for the detailed info, chem geek.

    My CYA is around 55. I swam in it myself last night and it felt great. No burning or irritations.

  12. Back To Top    #12

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

    Re: Is 10ppm FC safe to swim in?

    Quote Originally Posted by horsegal
    If I am understanding you correctly, it depends upon your CYA level as to what a safe FC swimming level truly is. I always thought that the degraded elasticity in swimsuits in indoor pools was more related to chloramine levels. Indoor pools always seem to have that "smell" that I thought was actually caused by chloramines, not free chlorine.
    Yes, you understand this correctly. Roughly speaking, it's the FC/CYA ratio that determines the equivalent FC with no CYA in terms of active chlorine.

    Chloramines are not powerful oxidizers so do not degrade swimsuits as quickly as chlorine though they aren't benign either and they aren't usually at very high levels (usually 1 ppm CC or less, even in indoor pools). The worst of the smell is when nitrogen trichloride is produced even in quantities as low as 0.02 ppm (20 ppb) and it turns out from the chemistry (detailed here) that higher active chlorine levels produce nitrogen trichloride at faster rates and in greater quantities over time or per introduced ammonia/urea from sweat/urine. There hasn't been any study proving this (no one has looked at this, especially looking at CYA), but it's one reason why lower chlorine levels are used in water treatment and in the German DIN 19643 standard for pools which is 0.3-0.6 ppm FC (they don't use CYA because they also completely remove chlorine and chloramines on each filter pass).

    So, yes, the smell is from chloramines, but it's often from the worst-smelling of the chloramines and it can be significantly reduced by orders of magnitude (10x or more) by using a small amount of CYA (around 20 ppm). At least that's the theory.

    Richard
    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
  •