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Thread: Breakpoint Chlorination

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    Breakpoint Chlorination

    I work at a large (860,000 gallon) high use pool and have had high levels of chloramines the last couple of weeks which started in the middle of a large swim meet with approximately 860 swimmers.

    We are coming up on another large swim meet and my combined chlorine is still running at .7 ppm. FAC = 2.4 ppm and TAC = 3.1 ppm

    I am considering breakpoint chlorinating the pool Saturday night in preparation for next week but I am worried that I will not be able to get the chlorine back down to a legal level before Monday AM when we are open to the community again.

    My plan is to breakpoint chlorinate Saturday evening. Then backwash to waste, vigorously, taking maybe 6 inches of water out of the pool on Sunday to reduce our chlorine levels due to fresh fill water before opening Monday.

    Do you think this will be enough water replacement / time to reduce our levels?
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    Re: Breakpoint Chlorination

    Breakpoint Chorination is not real, it is based on a flawed out of date understanding of how Chlorine works in a pool based on a theory made up by someone that was not a chemist. You can search to forum here on it, Chem Geek has written on the subject several times, hopefully he will chime in here.
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    Re: Breakpoint Chlorination

    Welcome to TFP!

    You can always super-chlorinate to speed up chemical reactions, but depending on what you've got in your water this can end up creating CC not just getting rid of it. If you do super-chlorinate, then strongly aerate your water and run your air systems full bore to try and evacuate the volatile organic compounds from the pool. If the chlorine level does not drop quickly enough, and with an indoor pool it probably won't, then you can use a dechlorinating chemical to lower it more quickly.

    The part about breakpoint chlorination that isn't true is the 10x rule. Higher chlorine levels will speed up chemical reactions, but there is no magic 10x. This was based on the total amount of chlorine needed to oxidize ammonia but is when ammonia is measured in ppm N (Nitrogen) units. CC is measured in ppm Cl2 (chlorine) units the same as FC so there is no factor of 5.1 units difference. Also, CC already has one chlorine attached. So forget the 10x part of the rule. As I wrote, you can raise the FC level as much as you want, but you do risk simply creating more CC which I suspect is mostly chlorourea anyway (especially if you don't smell any chloramines).

    Some pool operators use non-chlorine shock (MPS) to try and get rid of CC and organic precursors, but again that's iffy depending on what exactly is in your pool. Note that MPS itself will register as CC so needs the Taylor K-2042 to remove that interference.
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    Re: Breakpoint Chlorination

    Quote Originally Posted by Isaac-1 View Post
    Breakpoint Chorination is not real, it is based on a flawed out of date understanding of how Chlorine works in a pool based on a theory made up by someone that was not a chemist. You can search to forum here on it, Chem Geek has written on the subject several times, hopefully he will chime in here.
    Then how about taking advice from someone who is a chemist.

    http://dnr.wi.gov/regulations/labcer...eakpoint-c.pdf

    I believe this guy is a senior chemist with the state of Wisconsin. An excellent explanation of break point chlorination in his presentation.

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    Re: Breakpoint Chlorination

    Quote Originally Posted by freetothink View Post
    Then how about taking advice from someone who is a chemist.

    http://dnr.wi.gov/regulations/labcer...eakpoint-c.pdf

    I believe this guy is a senior chemist with the state of Wisconsin. An excellent explanation of break point chlorination in his presentation.
    It really has no bearing on what we do with pools here. I understand the theory, but it's irrelevant to us. When you are able to hold free chlorine you are able to hold free chlorine. We have no need to calculate that, or worry with it. I suggest that you read what we are about before you join this forum and open your first day by insulting one of our members. As you did in your second post I have now deleted. I can assure you that we don't tolerate treating people that way here. Because you disagree, does not mean you can insult people.

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    Re: Breakpoint Chlorination

    Breakpoint chlorination is very real, but as I wrote in my post the 10x rule-of-thumb that comes from it was misapplied to swimming pools with regard to getting rid of Combined Chlorine (CC). The link you gave to a presentation doesn't even go into the same level of detail as I do (in other posts) and doesn't even talk about the 10x part of breakpoint chlorination that is the part that is misapplied to CC in the pool industry. The presentation also has graphs showing chlorine concentration/effectiveness that do not apply when Cyanuric Acid (CYA) is in the water (i.e. the "Free Chlorine Distribution with pH" graph doesn't apply when CYA is present and I show the proper graphs in this post).

    So let's take this step-by-step and walk you through this. First of all, let's go through where breakpoint chlorination and specifically the 10x rule comes from since much of that information is not in the presentation you linked to. More detail is in the thread Chloramines and FC/CYA. It comes from adding chlorine to ammonia where initially there is more ammonia then there is chlorine. That is not a normal situation in swimming pools where chlorine levels are maintained and there is usually much more chlorine than ammonia. Nevertheless, the first step is the following:

    (1) HOCl + NH3 ---> NH2Cl
    Hypochlorous Acid + Ammonia ---> Monochloramine

    The above reaction occurs very quickly with 95% completion in a few seconds when no CYA is present or under a minute when CYA is present. By the way, in that presentation you linked to on the page entitled "How fast is chloramine formation?" it uses as an example for rates an HOCl concentration of 0.2x10-3 mol/l, but did you actually calculate how much this is? It's 14.2 ppm (mg/L) with no CYA which is quite high. That's why he gets 0.2 seconds at a pH of 7. In practice the levels are lower which is why I quote a few seconds for 95% completion, but the point is still the same that the above reaction is rather fast. If you were to open a pool with ammonia in it, you would find that the chlorine demand is very rapid and forms CC with no resulting FC, but that is NOT the situation in pools maintaining chlorine and having a bather load and it is not the situation described by the original poster in this thread where they already are measuring FC so clearly there is not ammonia remaining in the pool. So that brings us to the next series of equations that are much slower than the above.

    (2) HOCl + NH2Cl ---> NHCl2 + H2O
    Hypochlorous Acid + Monochloramine ---> Dichloramine + Water

    (3) HOCl + NHCl2 ---> NCl3 + H2O
    Hypochlorous Acid + Dichloramine ---> Nitrogen Trichloride + Water

    (4) NHCl2 + NCl3 + 2H2O ---> 2HOCl + N2(g) + 3H+ + 3Cl-
    Dichloramine + Nitrogen Trichloride + Water ---> Hypochlorous Acid + Nitrogen Gas + Hydrogen Ion + Chloride Ion

    The full set of Jafvert & Valentine equations including the above are in this Breakpoint spreadsheet I made. Initially, equation (1) dominates and is the fastest so monochloramine is produced. Then equation (2) grows in speed and dominates (because the monochloramine builds up and the ammonia declines) and equation (3) then occurs as well and then (4) so that all three equations (2,3,4) run together so that there is not a lot of dichloramine or nitrogen trichloride lasting very long as intermediates but this process takes around 10 minutes when no CYA is present (more than 90% complete with 2 ppm FC) or around 4 hours when CYA is present (with FC/CYA ratio 7.5%).

    The net reaction, ignoring some side reactions that go to nitrate, is the following

    3HOCl + 2NH3 ---> N2(g) + 3H2O + 3H+ + 3Cl+
    Hypochlorous Acid + Ammonia ---> Nitrogen Gas + Water + Hydrogen Ion + Chloride Ion

    You can see that there is a molar relationship of 3:2 for chlorine to ammonia. Chlorine is measured in ppm Cl2 units where molecular chlorine has a molecular weight of 70.906 g/mole whereas ammonia is measured in ppm N units where atomic nitrogen has a molecular weight of 14.0067 so in terms of a chlorine to ammonia ppm (weight) ratio it is (3*70.906)/(2*14.0067) = 7.593. In practice due to side reactions producing nitrate, the actual weight ratio needed for chlorine oxidation of ammonia is 8 to 10 and this is where the 10x rule-of-thumb comes from.

    Now let's look at how this very valid rule was misapplied in the pool industry. The pool industry took this rule and applied it against Combined Chlorine (CC). The first major flaw is that CC is measured in molecular chlorine units (i.e. ppm Cl2), NOT ammonia nitrogen units (i.e. ppm N). So there is no factor of 70.906/14.0067 = 5.062 weight difference. The second major flaw is that CC already has chlorine combined with ammonia presuming it is mostly monochloramine which should be the case if one starts with ammonia. So two of the 3 initial chlorine would have already been used up combining with the two ammonia. In other words, when starting with CC that is monochloramine, the net reaction is the following:

    HOCl + 2NH2Cl ---> N2(g) + H2O + 3H+ + 3Cl+
    Hypochlorous Acid + Monochloramine ---> Nitrogen Gas + Water + Hydrogen Ion + Chloride Ion

    So the molar ratio of what is left is only 1:2, not the original 3:2. In practice it would take a little more than this 0.5 amount, but the point is that it is nowhere near the presumed 10x rule.

    Even if one goes through this same analysis using chlorination of urea one doesn't get to more than 3x at the most. The 10x rule is completely wrong in its application to CC because 1) the unit of measurement of CC is 5 times larger than that of ammonia so takes 1/5th as much chlorine compared to ammonia and 2) chlorine is already part of CC so it takes less chlorine to further oxidize it.

    Finally, in pools breakpoint chlorination is continuous because chlorine levels are maintained. So there is no magic number whether it be 10x or 3x or 1x because one is not asking how much chlorine is needed to complete oxidation but rather is simply asking whether increasing chlorine concentration will make things go faster and make things better or worse. That's what I responded to in my post. Increasing chlorine concentration can have the CC decrease if the original chemical to be oxidized was ammonia, but the CC may increase if the original chemical to oxidize is urea because urea is much slower to combine with chlorine. There are other techniques for removal of organics precursors such as urea including flocculation/coagulation that may be more effective and of course supplemental oxidation (e.g. ozone) may be helpful.

    Where the breakpoint chlorination of chlorine added to ammonia does apply is when opening a pool in the spring to a huge chlorine demand when bacteria have converted CYA into ammonia (see Degradation of Cyanuric Acid (CYA)) where one can use an ammonia test kit to see how much ammonia is left to oxidize and here one can legitimately use the 10x rule-of-thumb to figure out how much more chlorine (FC) one needs to add to oxidize such ammonia. Note that one only uses this 10x rule multiplying the ppm N (or ppm NH3 which is close enough) from an ammonia test kit and NOT the CC amount if one already started adding chlorine since CC is in ppm Cl2 units and already has one chlorine attached to ammonia as monochloramine. However, in such degradation of CYA this will be an underestimate of the amount of chlorine needed since there is often partially degraded CYA still left (e.g. biuret, allophanate) and that doesn't show up in ammonia tests nor as CC.
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    Re: Breakpoint Chlorination

    I just found some small parts of the presentation were wrong. His comment that there is no test for CC, that it must be calculated is one.

    As to no CYA in the water, I wonder if WI prohibits CYA in commercial pools?
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    Re: Breakpoint Chlorination

    As noted in this NSPF list of state/county swimming pool codes, Wisconsin DHS 172.04 allows CYA and states the following limits to it in DHS 172.14 "Disinfectant feeding and residuals" (4) "CHEMICAL CONCENTRATIONS AND RESIDUALS" (b) "Cyanurates" (bold emphasis mine):

    The water cyanuric acid concentration may not exceed 30 ppm.
    Furthermore, in sub-section (e) "Combined chlorine" it states:

    When combined chlorine exceeds 0.5 ppm in an outdoor pool or 0.8 ppm in an indoor pool, the water shall be treated to breakpoint chlorination using a chlorine product or a nonchlorinated oxidizer such as potassium peroxymonosulfate. Isocyanurates may not be used to reach breakpoint chlorination. The pool shall be closed to the public during periods of breakpoint chlorination when a chlorine product is used.
    Note that they misapply breakpoint chlorination because they refer to CC and not ammonia. I'll write more about this later in this post.
    and section (f) "Maximum chlorine residual" states:

    The maximum chlorine residual in any pool shall not exceed 10 ppm.
    Furthermore DHS 172.17 "Water test kits" (1) states:

    A test kit of a type approved by the department shall be maintained for testing the pool water pH; the disinfectant residual; the combined chlorine level, when chlorine is used; the total alkalinity; and the cyanuric acid concentration, when used.
    and DHS 172.18 "Water testing frequency" (1) states:

    Except as provided under sub. (2) or (3), water shall be tested for pH and disinfectant residual daily before the pool is open to the public or before the pool is in use, and at least one other time during the day’s peak patron load. When chlorine is used, the water shall also be tested at least twice a week for the combined chlorine level. Water shall also be tested at least once a week for total alkalinity. When cyanuric acid is used in the water basin, the cyanuric acid concentration in the water shall be tested at least once a week.
    Pool Industry Gets It Wrong, Big Time

    The pool industry got it wrong decades ago and everyone has been following the 8x to 10x rule like lemmings ever since (again, the rule IS correct against ammonia in ppm N units). An example of this incorrect practice and then partial turnaround by those in the industry is found by first looking at the article Breaking Point: Using breakpoint chlorination to reduce chloramines may just be adding to the problem. New research shows why. Note that their graph for breakpoint chlorination explicitly says "Chlorine to Nitrogen Mass Ratio" for the X-axis which is where a factor of 5.062 comes from that does NOT apply when looking at CC which is in ppm Cl2 units (i.e. this would be a "Chlorine to Chlorine Mass Ratio"). They completely missed that fact.

    Then look at the article Is Superchlorinating The Best Way To Eliminate Chloramines? just two years later where again they refer to the wrong industry rule as taught by the CPO course (at the time):

    The standard procedure for dealing with chloramines is laid out in black and white in the CPO manual: You blast (shock) it with a high dose of chlorine — 10 times the measured amount of chloramines — and that takes care of that.
    :
    Breakpoint chlorination techniques are really only effective against inorganic, ammonia-based chloramines. They do not impact the organic chloramines present in all pool water.
    :
    In summary, Tufano says: "We should stop the practice of superchlorination. That just exacerbates the problem of forming disinfection byproducts that get into the airspace and degrade air quality especially indoors. We should restrict the amount of chlorine we apply to what is needed to sanitize the pool, as opposed to sanitation plus oxidation."

    "The concept of breakpoint chlorination, when applied to the real-world mixture of organic and inorganic chloramines in pool water does not work. High doses of chlorine result in high levels of chloramines which, in the end, give you large amounts of chlorinated DBPs."
    I wrote about the above in some detail in the thread Is the formula for "Superchlorination" or "Shock" too high? That thread referred to the 2009 Taylor Technologies article BREAKPOINT CHLORINATION FORMULA UNDER REVIEW INDUSTRYWIDE where it states:

    To greatly simplify their presentation, what Ed and Roy believe is that a breakpoint dosage of chlorine, as calculated according to current teaching (i.e., 10 times the measured level of combined chlorine), results in an over-application of chlorine because the formula doesn't account for the chlorine content of the combined chlorine compounds themselves. These compounds, our visitors explained, are already more than halfway to breakpoint. Instead, they support subtracting the existing level of free chlorine from the "10 times calculation" to determine the treatment dosage. They showed us research indicating the lower dosage would be sufficient to drive inorganic chloramines to breakpoint and leave a free chlorine residual.
    So let's sum up what the industry has supposedly "learned". They finally figured out that Combined Chlorine (CC) was already "more than halfway to breakpoint" because CC already had a chlorine attached. They also finally figured out that breakpoint only applied to inorganic chloramines starting with ammonia and did not apply to urea, creatinine, and other organic compounds. While that's great that the industry finally figured out those two points, they STILL have not admitted publicly to their biggest blunder by far which is the units of measurement difference between ammonia measured in ppm N vs. Combined Chlorine (CC) measured in the same units as chlorine, namely ppm Cl2. That's a factor of 5 error!

    Last but not least is the fact that the industry seems to think that if you do not add enough chlorine at whatever formula one uses for "breakpoint" calculation that somehow things get stuck and can't be fixed. That is not the way the chemistry works at all. You simply add more chlorine to get over the hump. Apparently the industry has a hard time distinguishing between stoichiometric quantities (i.e. how much one needs to add in total cumulatively and not necessarily all at once) vs. concentration (i.e. an FC level that is maintained).

    This distinction is demonstrated in what happens in pools opened up where bacteria converted CYA to ammonia. One simply adds chlorine quickly and if one sees the FC go away and CC form one simply keeps adding more chlorine until the FC starts to hold. One then keeps maintaining an FC level until the CC goes away. There is no need to blast with the full amount of FC needed, especially once FC starts to hold. Basically, even in the situation with ammonia, once one adds enough chlorine where FC starts to hold then that breakpoint chlorination process getting over the hump removing CC is continuous. And in the much more common situation of having a small amount of ammonia introduced into a huge body of water with chlorine in it, breakpoint chlorination is continuous. Nothing gets "stuck" if the FC level is too low. All that happens is that at lower FC levels (technically FC/CYA ratios when CYA is present), the process goes more slowly. If one has a lot of bathers, then the CC may rise because chlorine oxidation of bather waste is slower than the introduction of new bather waste. This is more of an issue for high bather-load commercial/public pools especially indoors than it is for outdoor residential pools.

    The largest nitrogenous component of bather waste is urea, not ammonia, so the biggest problem with CC in higher bather-load pools is mostly due to a buildup of urea in the water. Chlorine combines with urea rather slowly so urea concentrations can build up at which point the intermediate CC (monochlorourea) can show up. If you have a lot of built up urea and try to raise the FC level to get rid of the CC, the CC level may rise instead of fall. Some commercial/public pools try and deal with this by superchlorinating at night and then lowering the FC level for the morning. One aerates the water and runs fans to evacuate the very volatile and irritating nitrogen trichloride that is produced from chlorine oxidation of urea. As I mentioned in earlier posts, it would be better to remove urea itself either by supplemental oxidation (e.g. ozone, possibly UV if it breaks apart urea) or by coagulation/filtration (e.g. SeaKlear PRS Stage 1 & 2). Non-chlorine shock (MPS) can deal with organics other than urea (e.g. creatinine). In outdoor residential pools, the bather-load is low and the UV in sunlight breaks down chlorine into hydroxyl radicals that are short-lived but very powerful oxidizers and these may oxidize urea preventing its build-up. This is why we rarely see CC in our outdoor residential pools. In my own pool used almost every day for an hour or so with one person, I measure <= 0.2 ppm CC consistently (and it seems to really be <= 0.1 ppm CC below the quantization level of the test) and this is in spite of having the pool covered when not in use, but it is at least partly exposed to sunlight when in use.
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    Re: Breakpoint Chlorination

    Chem Geek,

    The quoted, "We should restrict the amount of chlorine we apply to what is needed to sanitize the pool, as opposed to sanitation plus oxidation." seems contrary to TFP practice..... Is it?

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    Re: Breakpoint Chlorination

    For our low bather-load pools we don't worry about oxidation very much. Remember that one person-hour in 10,000 gallons (assuming 4 grams chlorine demand per bather-hour) is only 0.11 ppm FC of chlorine demand. The vast majority of chlorine loss in our outdoor residential pools is from sunlight. So the amount of chlorine added each day is mostly to make up for that loss.

    As for the FC/CYA level we target, we set that to prevent green and black algae growth regardless of algae nutrient (phosphate and nitrate) level. That is higher than needed for appropriate disinfection (at least for residential pools where the risks are far lower). So their statement doesn't apply to our pools since they are talking about commercial/public high bather-load pools where the vast majority of chlorine usage is for oxidation of bather waste. What they are saying is that instead of setting a higher FC level to try and oxidize such waste faster and keep CC lower, they should instead use supplemental oxidation systems so that the FC level can be set lower for just disinfection. Remember also that the industry doesn't have a clue about the chlorine/CYA relationship so their statements generally have to be taken in the context of pools with no CYA.

    Now as for what they mean by a lower FC level for disinfection is debatable. If one goes by the EPA DIS/TSS-12 standard, then that's 0.4 ppm FC with no CYA (at pH 7.5) which is about 7 times higher than our minimum FC/CYA level (this is similar to the German DIN 19643 standard if one accounts for its lower pH). If one goes by the FC/CYA levels allowed in some state pools which would be as low as 1 ppm FC with 100 ppm CYA, then that is about 8 times lower than our minimum FC/CYA level. The sweet spot for disinfection for everything except protozoan oocysts (especially Crypto) is probably around an FC/CYA ratio of 2% to 3%, but that's not enough to prevent algae growth without using algaecide or phosphate remover (or being lucky enough to start with water low in phosphates). Even if a standard for commercial/public pools is set at a 20% FC/CYA ratio which would handle all algae growth including yellow/mustard algae and would only be half the EPA level, that would be far better than the situation today in such pools with no CYA including many indoor pools that with only 1 ppm FC and no CYA have at least 5 times this level of active chlorine and oxidize swimsuits, skin, and hair that much faster and produce disinfection by-products that much faster.

    If we wanted to minimize our active chlorine level further at TFP, then we'd need to do something to prevent algae growth (i.e. algaecides or phosphate removers). I wouldn't go much below the 2% to 3% FC/CYA ratio so that the kill times were still reasonable for fecal and most other bacteria and for many viruses (roughly 4 to 7 times slower than the times shown in this post). Remember that the risks in private pools are so much lower. So it's reasonable for commercial/public pools to have higher active chlorine levels in the 10% to 20% FC/CYA ratio range. Crypto has to be dealt with in other ways since even the EPA levels don't kill it fast enough. That's why the CDC Model Aquatic Health Code (MAHC) proposes using supplemental systems such as ozone or UV to deal with Crypto via circulation. That won't prevent direct person-to-person transmission, but it will at least prevent an outbreak from lasting over days or weeks before it gets figured out.

    The place where their statement does apply to residential situations is in spas since the bather-load can be quite high if they are used every day or two. In that situation, most of the chlorine is used to oxidize bather waste. In between soaks, however, the chlorine level is kept lower, but right after a soak a lot of chlorine is added to oxidize the bather waste. This is where an ozonator can help cut that chlorine usage roughly in half if the spa is used every day or two. Unfortunately, ozone also reacts with chlorine so in between soaks if the spa isn't used frequently the chlorine demand is at least doubled due to the ozone. The ideal situation would have the ozonator turn on right after one ends one's soak and stays on for 12-24 hours depending on how long it takes to oxidize the bather waste. The ozonator would then turn off until after the next soak. That way chlorine can be kept at a low 1-2 ppm FC level with 30-40 ppm CYA the entire time so provides for disinfection in the background but is not the primary chemical used for oxidation of bather waste. It's really too bad that MPS doesn't deal well with ammonia or urea and that it interferes in the chlorine tests; otherwise it would be reasonable to use it in conjunction with chlorine. If enzymes could be demonstrated to be effective against urea, then they would be another potential option.
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    Re: Breakpoint Chlorination

    Thanks for the clarification! I grabbed a cheap copy of the Aquatic Facility Operator Manual and have gained enormous admiration for large facility operators. There's a ton of stuff going on behind the scenes and with schedules and events (massive bather load) I don't know how they do it. I guess some don't do a very good job, but that it all works, is amazing....

    One thing to consider for some of us home pool folks is the locations of our pools... every one will be different, but I am in a heavily wooded area, in a coastal region, and next to a river. I think my "organic load" rivals, if not exceeds, bather load. Yet, our challenges still pale in comparison to the AFO.....

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    Re: Breakpoint Chlorination

    The maximum bather-load allowed varies by state. Most have roughly 15 square feet per bather in the shallow end and 20 square feet per bather in the deep end (away from diving areas). However, some codes allow down to 8 square feet per bather in the shallow end and 10 square feet per bather in the deep end. If I assume a 3' shallow end then 15 square feet would be one bather per 337 gallons. In the deep end assuming 6' then 20 square feet would be one bather per 898 gallons. Generally speaking, high bather load is one bather in less than 500 gallons of water. For a bather, not a competitive swimmer, 4 grams per hour would be the chlorine demand so this translates into 3.1 ppm FC per hour with a full pool that is all shallow end. In practice it is not uncommon for busy facilities to use at least 10 ppm FC per day. So bather-load dominates their chlorine usage.

    The problem is that when the facility uses chlorine alone to try and oxidize all of this bather waste, it can produce a lot of disinfection by-products and in pools not using CYA yet being outdoors exposed to sunlight, they get a lot of chlorine breakdown to hydroxyl radicals so help with oxidation, but are also more damaging to everything in the pool including swimsuits, skin, and hair, both from these radicals and from the higher active chlorine level. New York state is the only state in the nation to ban CYA completely for commercial/public pools, but that means every commercial/public pool exposes its patrons to far higher active chlorine levels than necessary. In most other states, it's the indoor pools where this occurs but without the sunlight it's only the high active chlorine level that is present.
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    Re: Breakpoint Chlorination

    I wanted to add for the none chemist and for people that just want to get their pool chlorine to a sustainable level.
    I have been helping my daughter with her new 22,000 gallon pool, this is her second year and she could not get her chlorine level up no matter how much chlorine she would add. She added two to three times the amount and the next day it still read zero. After I did research I found information on break point and what I did I wanted to share in case someone else had similar problems. I kept on adding chlorine until I ended up with a stable measurement. What was extraordinary is I used 9 pounds shock 55% cal hypo and 6 gallons of 8% bleach. I kept on going back to the hardware store getting 2 gallons at a time after running out of the shock. I ended up with about 5 ppm the last two gallons of bleach from a zero. It has been maintaining a 3 for over a week. I could not find any similar story anywhere and wanted to share the success. I believe the trees and shrubbery and the use too many organics were in the pool and the addition of all this chlorine was necessary to overcome, and the advice I would give if others were having the same problem is do a break point test to determine what is necessary, it would of saves us a lot of running around and saved us money in the long run, but you don't know until you run in to this problem.

  14. Back To Top    #14

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    Re: Breakpoint Chlorination

    Quote Originally Posted by chem geek View Post
    However, some codes allow down to 8 square feet per bather in the shallow end and 10 square feet per bather in the deep end.
    How do you handle a situation like this from an operator's perspective?

    INSANE wave pool in Tokyo. Wheres the water? - YouTube
    20k gal. IG plaster w/spa. 2 HP Aqua-Flo "A" pump, Hayward DE6020 filter. "The Pool Cleaner".

  15. Back To Top    #15

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    Re: Breakpoint Chlorination

    Welcome to TFP!

    We actually have a LOT of stories similar to this and understand what is going on. My own situation with this is described in the thread It Can Happen to Anyone - Zero Chlorine, CYA-->Ammonia and is described technically in the section "CYA Degradation by Bacteria" in the thread Degradation of Cyanuric Acid (CYA). Every season there are a number of people opening their pools in the spring after having let them go (i.e. not chlorinating them) and quite a few have CYA dropped significantly even to zero. For the fortunate ones, they do not have unusually high chlorine demand upon opening indicating that bacteria may have converted the CYA to nitrogen gas or to nitrate. However, for the unfortunate ones, the bacteria convert the CYA into ammonia and that creates a HUGE chlorine demand and follows breakpoint chlorination.

    Of course, the breakpoint chlorination "10x" rule only applies to the ammonia measured in its own units of measurement (ppm Nitrogen). Also, because the bacterial degradation of CYA may not be complete, there may be partially degraded CYA that will not show up in ammonia or CC but will require more chlorine to oxidize. So you can do a bucket test to determine the total chlorine demand or you can just keep adding chlorine to the pool until the FC starts to hold though it may be in two phases -- the first where the chlorine is consumed very quickly (in less than a minute) as it converts ammonia to monochloramine and then a slower second phase that takes hours where it converts monochloramine to nitrogen gas (about 4 hours if CYA is in the water) or oxidizes partially degraded CYA.
    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"

  16. Back To Top    #16

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    Re: Breakpoint Chlorination

    Quote Originally Posted by sbcpool View Post
    How do you handle a situation like this from an operator's perspective?

    INSANE wave pool in Tokyo. Wheres the water? - YouTube
    Our codes down to 8 square feet per bather would be a square 2.8'x2.8' or a circle with radius 1.6' so maybe counting the size of the inner tube that insane wave pool is actually within some of our code limits!
    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"

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