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Thread: pool store test says tot. cl is 10???

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    pool store test says tot. cl is 10???

    Hi, Im on the winning side of a Alge struggle it is almost clear, used nothing but Walmart bleach and Arm and Hammer so far...

    The kids asked if they could go in it today I was wonderin' it was ok...

    Thanks and Peace

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    MikeInTN's Avatar
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    Re: pool store test says tot. cl is 10???

    It really depends on your CYA level, and what part of that total chlorine is free chlorine. Any idea of what your CYA and FC is?
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    Re: pool store test says tot. cl is 10???

    Quote Originally Posted by MikeInTN
    It really depends on your CYA level, and what part of that total chlorine is free chlorine. Any idea of what your CYA and FC is?
    I've been wondering about this. I understand that the FC level necessary to keep a clean pool changes based on your CYA level. It seems like to me as far as safety goes, the only thing that would matter is the FC level. The recommendations I've seen on this board is that it is safe to swim when FC is <10. I thought that the FC/CYA relationship was strictly for determining the amount of chlorine need for it to be able to do its job.
    20,000 gallon gunite pool, attached spa, Pebblesheen finish, Paramount PCC-2000 infloor cleaning system, Paramount ClearO3 ozone system, Intelliflo VS main pump, Whisperflo 1HP cleaner pump, StaRite cartridge filter, StaRite heater

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    MikeInTN's Avatar
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    Re: pool store test says tot. cl is 10???

    It all depends on your CYA level, because CYA "locks" up FC. For a CYA of 30, your recommended FC is 2 - 6; for a CYA of 90, it's 7 - 12. However, the actual amount of FC that's available to sanitize the pool is the same.

    You'll get varying opinions on what the "safe" level of FC is; I just read a post where Jason says he's comfortable with anything under shock level for the given level of CYA, but the key words there are what he's comfortable with. If you're not comfortable with your kids swimming with an FC of 10, then make sure you keep your CYA level down to where FC< 10 is an acceptable amount for sanitation.
    24' x 52" AGP - approx 13,500 gallons
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    Intex 8110 SWCG
    "Fear the Schnauz!"

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    Re: pool store test says tot. cl is 10???

    Chemgeek has a great, detailed explanation on this. With CYA, the effective chlorine is greatly, greatly reduced.

    I can't remember the exact numbers but something like [FC=15......CYA=40] is not stronger then [FC=2.....CYA=0]

    I'm making up those numbers but I am reasonably close, I think.

    I wouldn't hesitate to swim in a 25ppm FC pool if I had 30 or so CYA. Others suggest more caution.
    Dave S.
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    Re: pool store test says tot. cl is 10???

    Maybe I'm being dense, but I still don't understand how CYA has anything to do with the safety level of chlorine. I'm not talking about the chlorines effectiveness to clean the pool, but just the safety of swimming in high levels of chlorine.

    To me, with a high level of CYA, you would have to have a very high level of chlorine to keep the pool clean. I just wouldn't want to swim at chlorine levels of 15-20. At really high CYA, I would think to safely swim in the water, you would have to keep the chlorine as a lower level than the CYA/Chlorine chart would say and then use an algecide to help keep the pool clean.

    Not trying to be argumentative, I just really don't understand and trying to understand this.
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    Re: pool store test says tot. cl is 10???

    Chlorine doing its job, and swimmer safety (as it regards chlorine levels) are no different. The chlorine's job is to kill stuff. Safety for swimmers is not really any different than safety for bacteria or safety for algae, except that people can withstand higher levels than bacteria.

    CYA alters the effective level of chlorine. As you know, as the CYA gets higher, the more overall chlorinator is needed to keep an effective sanitizer level in the pool. With a CYA level of 40, an FC level of 15 works out to an effective level of about FC=2 or so, not 15. It is that FC=2 is what you, your swimmers, your bacteria, and your algae will experience, regardless of what the test kit shows, because the test kit does not compensate for CYA. You're not really swimming in FC=15, but in FC=2 because of the CYA. It'll kill the microscopic critters, but not the kids.

    So the point is that it's the dose that makes the poison. The concentration amount of effective chlorine compared to the body mass of whatever gets into the water, is what makes it lethal (for bacteria) or not noticeable (for humans).
    [center:1kpalu48]Helpful Links: Pool School | CYA/Chlorine Chart | Pool Calculator[/center:1kpalu48]

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    Re: pool store test says tot. cl is 10???

    Think of the FC as mostly measuring the chlorine capacity or that held in reserve, but only the amount of chlorine that isn't bound to CYA (and is the more potent of two forms -- namely, hypochlorous acid) is "active" or powerful. Think of an army of soldiers where only those on the front line are "active" and have guns. The fact that you've got many more soldiers in reserve not fighting is irrelevant in terms of how quickly the soldiers kill the enemy. The reserve only tells you how long you can continue to fight when "active" soldiers die killing the enemy and get replaced from the reserve.

    The shock levels of chlorine where the FC is around 40% of the CYA level are technically equivalent in "active" chlorine concentration to that found in 0.6 ppm FC with no CYA. The "active" chlorine concentration is not only what kills bacteria, viruses and algae, but is also what oxidizes swimsuits, skin and hair. My wife experiences this effect every year when she swims in an indoor community center pool over the winter that has 1-2 ppm FC with no CYA and her swimsuits degrade (elasticity gets shot) every season so she has to get new suits; also, her skin is flakier and hair frizzier. In our own outdoor pool with 3-4 ppm FC and 30 ppm CYA, the swimsuits have lasted for many summer seasons with no degradation and her skin and hair are far less affected. The difference is that our pool with CYA is equivalent to 0.1 ppm FC with no CYA so the indoor pool has 10-20 times the active chlorine concentration and is degrading her swimsuits, skin and hair 10-20 times faster than in our outdoor pool.

    There IS an affect on human health with FC alone regardless of CYA level and that is if you were to drink the pool water. In this case, it is the chlorine capacity that is more relevant than its reaction rate. This is because there are lots of compounds to react with in saliva and in the body and plenty of time to do so. The CYA may slow down these reactions, but they keep on occurring and the water is in your system long enough that it is the FC or total capacity of chlorine that is relevant in terms of how many chlorine by-products your body will eventually get exposed to (though technically some by-products are formed more when the active chlorine is higher). Even so, the EPA rule of 4 ppm FC being a limit in drinking water is for drinking many quarts of water EVERY DAY. You aren't normally drinking very much pool water, even if you accidentally took a gulp.

    There is some dermal absorption of pool water, but what I can find it's relatively low and the chlorine tends to react with the skin surface before it gets in any deeper, though technically having no CYA would use up the chlorine more quickly before it got too far. It's hotter water as in showers and spas that have the pores opened up more and it's also when there's more water (and its contents) that are inhaled. Even so, this shower issue is subject to debate and there haven't been studies correlating ill effects. Also, using CYA will reduce the outgassing of chlorine as well as the production of the most volatile disinfection by-products (e.g. nitrogen trichloride). Virtually all of the respiratory and ocular problems associated with pools are indoors and I suspect without CYA.

    Richard
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    Re: pool store test says tot. cl is 10???

    Thanks ChemGeek. I didn't realize that there was a difference in Chlorine that is bound to CYA and Chlorine that isn't. I have just assumed that all Chlorine showed up as FC, assuming CC is 0. So for example, if my CYA level is 40, the target FC based on the CYA/chlorine chart is 5. I've assumed all 5ppm of FC would be active. Are you saying that some part of that FC level is bound to CYA and some is free to fight? Also, if the chlorine that is bound to CYA is a reserve, how does it get released from the CYA to become active?

    I'm not even sure these questions make sense but hopefully, you're understanding why I'm confused.
    20,000 gallon gunite pool, attached spa, Pebblesheen finish, Paramount PCC-2000 infloor cleaning system, Paramount ClearO3 ozone system, Intelliflo VS main pump, Whisperflo 1HP cleaner pump, StaRite cartridge filter, StaRite heater

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    Re: pool store test says tot. cl is 10???

    There is always some percentage of the chlorine bound to CYA. What the percentage is depends on the CYA level. The higher the CYA level, the higher the percentage that is bound to CYA. When the active chlorine gets used up, some of the chlorine that is bound to the CYA unbinds, until the correct percentage is unbound or you run out of chlorine.
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    Re: pool store test says tot. cl is 10???

    I'm always learning things reading the posts here. I use the charts here as guides as to how much FC I should have in the water given a particular CYA level, and I'm definitely aware that higher CYA levels require higher FC levels because more CYA means a higher percentage of the FC is "blanketed" and less is "active", but I had no idea just how little of the FC was "active". For instance, it was a real eye-opener to read that 3-4 ppm FC with 30 ppm CYA resulted in an active chlorine level of only 0.1 ppm! I had always thought that we wanted an "active" level of around 1 ppm, but I guess that's way more than necessary (I was surprised also to read that the shock levels are equivalent to only 0.6 ppm of active chlorine). Interesting stuff to read and know...thanks again!

    Are there charts and/or formulas available here to calculate the equivalent level of active chlorine, based on FC and CYA levels in the pool? And is 0.1 ppm "active" chlorine a typical level required in the pool to effectively sanitize and prevent algae?

    Thanks,
    Greg
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    Re: pool store test says tot. cl is 10???

    If you dare tackle advanced chemistry, take a look at Pool Water Chemistry. There are graphs and tables with the info you are looking for, though I don't think the actual equation is ever spelled out.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: pool store test says tot. cl is 10???

    Wow, now I've got a little more reading to do. This has really helped my understanding of the process and has helped me understand the CYA/Chlorine chart versus just understanding how to use it. Is there a place on the web site where the "Pool Water Chemistry" link is saved?
    20,000 gallon gunite pool, attached spa, Pebblesheen finish, Paramount PCC-2000 infloor cleaning system, Paramount ClearO3 ozone system, Intelliflo VS main pump, Whisperflo 1HP cleaner pump, StaRite cartridge filter, StaRite heater

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    MikeInTN's Avatar
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    Re: pool store test says tot. cl is 10???

    Quote Originally Posted by Woodberg
    Thanks ChemGeek. I didn't realize that there was a difference in Chlorine that is bound to CYA and Chlorine that isn't. I have just assumed that all Chlorine showed up as FC, assuming CC is 0. So for example, if my CYA level is 40, the target FC based on the CYA/chlorine chart is 5. I've assumed all 5ppm of FC would be active. Are you saying that some part of that FC level is bound to CYA and some is free to fight? Also, if the chlorine that is bound to CYA is a reserve, how does it get released from the CYA to become active?

    I'm not even sure these questions make sense but hopefully, you're understanding why I'm confused.
    Woodberg, here's a link to a discussion that was held not too long ago in The Deep End about the chlorine/CYA relationship. Richard aka Chemgeek explains the equilibrium that exists between hypochlorous acid ("active FC") and the chlorine bound by CYA.

    and for the record, when I grow up, I want to be just like Chemgeek and JasonLion and Waterbear and John T and Waste!! Those guys rock!!
    24' x 52" AGP - approx 13,500 gallons
    Pentair Optiflo 1 hp/2sp pump w/ Swimpro Voyager 150 sq ft cartridge filter
    Intex 8110 SWCG
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    Re: pool store test says tot. cl is 10???

    In Pool School, the final article, Further Reading, is a list of links to helpful posts. There are two or three advanced chemistry articles in that list.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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