Bartier Disinfection Index

[smallpooldad]

Any views on this index (link below)? If it is useful? If so can Ben's excellent calculator for CYA be adjusted for shocking?

Is it correct or not, that temperature also has an effect on the strength of chlorine; or are the numbers not that meaningful?

I created a simple excel spreadsheet and if you run the numbers on a pool with 70 CYA, 3 FC, and a pH of 7.9 it is scary. Looks like all the people I know in Hawaii who have saltwater pool and stick to these numbers need to buy life insurance. "I'm swimming in my own private ocean, my dear." This maybe true but an ocean of what?


http://www.caromal.co.uk/Resource%20Page%205.htm

Looking forward to your replies.

[waterbear]

In the pH range of 7.4 to 7.6 the cholrine is aprox. 50% as hypochlorus acid (actually 52% to 42%) so this is just showing how important it is to keep the pH in line along with the FC and why both need to be tested for more frequently than the other tests!

Your pH of 7.9 is out of accepted range. 7.2 to 7.8 is considered acceptable with 7.4 to 7.5 condsidered 'ideal'. CYA will lower the effectiveness of chlorine but it will keep it around longer in the sun. It still works but not as well as hypochlorous acid does.

[smallpooldad]

Thanks Waterbear,

I may have confused you by posting those numbers. They are more typical of our local saltwater pools, here in Hawaii. Does this mean all the rich people are done for?

Mine is as follows:

Plaster pool (no salt)
CYA 40
FC 5
ALK 100
pH 7.4
Calcium 260
TDS 740

[duraleigh]

Guys,

Ben's philosophy from the beginning has been to keep general pool maintenence within reach of the average person......this post won't help.

This belongs over in the "techno-geek" section of the China Shop forum!
I sometimes wander over there and read some of the postings, but I'm afraid most of them are over the head of this 'ole country boy. :)

[waterbear]

All the Bartier Disinfection Index is saying is that your pH is important at how well your chlorine works and that too much CYA is a bad thing. It also gives a disclaimer that it is most usefull on commercial pools that are having problems!
If you keep your numbers in line you are following it automatically!

Salt pools with a genterator seem to work better with higher CYA and lower FC levels (WHEN the pH is kept in range!) because of the way the chlorine is introduced into the pool (or so I've been told by the Tech Support rep at Goldline Controls).

[smallpooldad]

Duraleigh,

I'm not sure that safe sanitization levels belong in the China Shop forum.

I do agree with you that keeping it simple is good.

Adding two numbers and subtracting one is hardly major programming, even for Good Ole'Boys.

It might help by reinforcing Ben's calculator with a simple scientific index keeping those persons healthy who are out of range especially the high CYA, low Cl and high pH persons who own saltwater pools of which there are many here in Hawaii.

This persons are often suspicious of anything but pure science, I live next to one such person. But then again you may be right, even that might not work with them as Voltaire said, "A fool will not listen and a wise person does not need to know." In the middle I have always believed that there are the uninformed like me that is why I visit this forum.

Aloha

[waterbear]

It might help by reinforcing Ben's calculator with a simple scientific index keeping those persons healthy who are out of range especially the high CYA, low Cl and high pH persons who own saltwater pools of which there are many here in Hawaii.

Aloha Yes, the CYA level in a Salt pool is high for the FC level but the chlorine is being introduced into the water at such high concentrations in the cell that it is constanly being superchlorinated when the cell is generating. Comparing this to a pool being manually chlorinated is comparing apples to oranges.

As far as pH goes. If they are letting their pH get up to 7.9 that is just bad pool maintenance since EVERY SWG manufacturer I have ever seen recommends keeping the pH at 7.2 to 7.6, some even specify 7.2 to 7.4! The pH, as you have seen with the Bartier index, is the MOST important factor.

[smallpooldad]

Good point.

Sadly, they often maintain their pools once a week with a pool person and I'm not sure if the pool persons are trying to save money on chemicals or just not visiting enough.

That is why the results are as described. The natural tendency in Hawaii is for the poolwater to rise rather quickly to a pH of 8.0 in most pools, keeping it at 7.4-7.5 is a major undertaking, I know I do it every day.

Anyway I'm giving up on saving the world.

But I did find it interesting that as I keep my pool sooooooo clean that my eyes were irritated slightly when swimming, could not understand why. It seems that my chlorine level is a tad too high using this index. So I learnt something new and am going to adjust accordingly.

Aloha and thanks for your help.

[sailork]

DOH!!! I'd just cleared up a mustard algae problem by bringing my pH way down to 7.8 (oh yea, i'd let it creep up a bit...) This index makes it obvious why that worked and why the SWG people seem to have fewer problems with algae etc. The pH of pure saltwater is 7.0. The SWG manufacturers tell the owners to add HCL (muriatic acid) to keep the pH below 7.6 or even 7.4. Thus their pools are much more disinfected. I'll have to find a cheaper source of HCL. That should be easy here in Texas' Chemical Coast. ;-) Those trichlor pucks with their very low pH are looking a whole lot better as well!! Thanks and Aloha!

[let_her_flicker]

At the old forum, Ben talked about people successfully operating pools with a High PH, above 7.8 I do not remember the particulars of that post, but I don't get nervous when my creeps above 7.8. I do bring it back down to the 7.5 level. Maybe Ben could chime in on that when he gets the time, but I do remember it not being a big deal as compared to high CYA.

But then again, at the old forum, he also talked about running high CYA pools and only having to sanitize once a week (as long as there wasn't some event the made you have to shock your pool). It did require you to have to do the DPD test to check Cl levels and required close monitoring to insure you did not let Cl get so low that you had a algae bloom.

I am sure CarlD remembers and can contribute on the point of high PH and high CYA pools. Yes, I understand pool operating should be simple and I do not operate my pool that way, but it can be done.

[mwsmith2]

Any views on this index (link below)? If it is useful?

Well, there is a relationship between pH, temp, Cl and CYA. It's true as CYA and pH climb, the 99% kill time increases. Is this one correct? Who knows, I'd have to check in to it further. Ben might be able to provide some insight.


If so can Ben's excellent calculator for CYA be adjusted for shocking?

Well, first off, it's not Ben's calculator, it's mine. :) (unless you are refering to his "best guess table, of course) Until this Bartier index is proven out, I'm not putting it in. I'd just hate to steer people in the wrong direction. The basic idea is consistent with the actual science I've seen, but I'm just not sure how consistent it is.

Michael

[PoolDoc]

If you'll go to Bartier's page, you'll see the display of the simple HOCl / -OCl curve, which correlates HOCl concentration to pH. His index is based on this curve. There are all sorts of problems with that.
The assumption that sanitation is provided by HOCl, and not -OCl, is not supported by field research. HOCl *is* a stronger sanitizer under SOME conditions than -OCl, but this fact doesn't always correlate with what's observed in actual pool simulations.
The simple curve he works from does NOT apply to outdoor pools with stabilizer. In those pools, the curve is radically different, and far more complex. One of my users is developing a *very* complex Excel spreadsheet that calculates HOCl, -OCl and other levels, based on CYA, DPD chlorine, pH, temp, & ionic solution strength. The calculation involves iterative simultaneous solution of 15 (I think) equations. My 'best guess' table is based on some *rough* approximations of this information, along with some adjustments based on field experience.
Bartier generally assumes that some of the simplistic metrics available to the pool industry are literally and absolutely applicable to actual pools, in spite of the wealth of information to the contrary. His pages are useful, if compared to information provided by Biolab or by pool dealers, but still leave much to be desired.All in all, I don't see any particular benefit from this discussion for most of the newbies coming here . . . so I'm moving this to the China Shop.

Ben

[smallpooldad]

Ben and Michael,

Thank you both, I think I will stick with your tables. Only one thing it did seem that there was less irritation to the eyes when the Cl dropped to Bartier's recommended level or is this purely a function of not enough CL?

Aloha

[chem geek]

I am the user that Ben mentioned who created the spreadsheet that accurately calculates the chlorine species in water including the chlorinated cyanurates.

With regards to the Bartier Disinfection Index, the pH Factor table is reasonably accurate and simply describes the HOCL to OCl- ratio that is independent of CYA (the RATIO is independent of CYA, but the absolute levels are certainly not).

However, simply subtracting the CYA level from the disinfection index is NOT an accurate way of predicting disinfection (assuming disinfection is directly related to the concentration HOCl as appears to be the case). There are two primary problems with the Bartier formula. First is that with no CYA it sets the minimum chlorine levels too high as required for disinfection (see below), though this level and even higher IS required for a reservoir of chlorine. For outdoor pools exposed to sunlight, you'd have to continually add chlorine as half of it could be gone in a half-hour. Second, their formula woefully underestimates the effect of CYA on reducing HOCl concentration (and therefore on reducing disinfection ability).

I won't put in the whole CYA/FC/HOCl table into this post (I'll create a new China Shop forum topic instead) but results from a commercial spas study and HOCl vs. ORP correlation data from a reliable ORP sensor manufacturer indicate that a 0.011 ppm HOCl concentration is the minimum required for disinfection and roughly corresponds to 650 mV ORP (at pH 7.5). Of course, prevention of algae may require more (this is part of what I want to find out from forum users). The "Ideal" Bartier Disinfection Index value of 91 implies the following levels of chlorine at different CYA levels and a pH of 7.5 (and I also show the calculated ppm HOCl):

CYA ..... ppm FC ..... ppm HOCl
.. 0 ....... 1.9 ............ 0.916
. 10 ....... 2.1 ............ 0.109
. 20 ....... 2.3 ............ 0.052
. 30 ....... 2.5 ............ 0.036
. 50 ....... 2.9 ............ 0.024
. 70 ....... 3.4 ............ 0.020
100 ....... 4.0 ............ 0.016

As you can see, a small amount of CYA will store (in chlorinated cyanurates) most of the total chlorine. The Bartier "VERY LOW" level of 50 with a CYA of 100 results in a ppm HOCl of around 0.011 so everything in their table does provide for minimum disinfection (which is good), but their "equivalency" of chlorine levels at varying of CYA is wrong. Also, I suspect that 0.03 or 0.05 ppm HOCl may be needed to prevent algae and if this is the case, the chlorine levels they propose at high CYA would be too low.

Ben's table is a better guide to chlorine requirements vs. CYA since it more closely tracks a minimum level of 0.02 ppm HOCl though the mid-points of the ranges are closer to 0.05 ppm HOCl. It's nice to know that real-world experience has a basis in chemical theory (or vice versa). As Ben mentioned elsewhere (on another forum), the shock values are not as consistent, but we really need more real-world experience to know what minimums are truly required to zap algae at various CYA levels.

Richard (aka "chem geek")

[chem geek]

With regard to HOCl vs. OCl- as a sanitizer, there appears to be valid science to back the notion of HOCl being the more powerful sanitizer for certain kinds of bugs. This is because most pathogens have cell walls that are negatively charged as follows:

1) Gram-Positive bacterial cells (so named due to a positive result from a stain test developed by Hans Christian Gram) have teichoic acids (phosphate groups joined by glycerol or ribitol) that give a negative charge to the outer cell wall.
2) Gram-Negative bacterial cells have lipopolysaccharides that give a negative charge to the outer cell well.
3) Many, but not all, viruses have a net negative electrical charge since their viral envelopes often come from host cells (which have a negative charge on their cell wall). Viruses enter cells at specific binding sites that overcome the electrostatic repulsion.

Since HOCl is neutral, it is more readily able to enter cells than OCl-. Polar molecules and ions generaly only enter cells through specific channels that only allow ions of certain sizes and shapes generally blocking OCl-. On the other hand, algae have different types of cell walls like cellulose that does not appear to be charged. So while HOCl may be a more effective sanitizer for bacteria and viruses, it may not be more effective for algae, but I cannot confirm that.

(See WHO water sanitation document (http://www.who.int/water_sanitation_health/dwq/en/watreatpath3.pdf))

Once inside a cell, the mechanism of sanitation appears to come down to two different mechanisms though this appears to be somewhat speculative:

1) Chlorine substitution where the HOCl substitutes its chlorine with hydrogen from an organic compound (a protein, typically an enzyme). This substituion inteferes with the enzyme's function (folding of protein, intereference of active site, etc.).
2) Chlorine oxidation of organics (typically from production of free radical oxygen O• from HOCl or OCl-). This can destroy proteins (including enzymes) as well as DNA (typically during cell division).

The dependence of Oxidation-Reduction Potential (ORP) on pH that follows the concentration of HOCl plus my analysis of the commerical spas study (Oregon) data using HOCl lead me to believe that HOCl is indeed the effective sanitizer against bacteria. I couldn't find scientifically valid information on algae to know whether HOCl or OCl- is more effective, but in any event I would doubt that OCl- is more effective than HOCl even for algae (though it might be about equally effective -- I just don't know).

[waterbear]

There is one other factor to look at with pH when killing algae. If the pH is on the high side it will favor the formation of monochloramine when the chlorine combines with ammonia in the water. Chloramines are nitrogenous compounds and the algae will consume them as food. It is by this mechanism that 'chlorine enhancers' (inorganic ammonia based) are supposed to work. This makes the situation a bit more complex than just looking at the ratio of HOCL to OCl- based on pH since other reactions and substances become involved and are also pH dependant.

[chem geek]

Evan (waterbear),

Thanks for the info on chloramines and their use in killing algae. I did read something about this in some non-scientific articles, but couldn't find good data on algae kill levels (for different algae types) for either chlorine (HOCl) or chloramines (NH2Cl) except for an EPA report that essentially said that 0.1 ppm chlorine (in sea water, so chloramines certainly were formed) killed most marine plankton. On the "Save Swimming with Elevated Chlorine" forum you mentioned that there were studies showing the relationship of ORP to different types of algae that grew in that environment -- I would appreciate links to those studies or a summary of results and whether there was ammonia present (so that chloramines would have formed), what the pH was, etc. I can roughly translate ORP to ppm HOCl at least to get an idea, both for maintenance and shocking.

You also commented on the other forum (if I should respond there instead, let me know) about the use of ORP sensors and how these measure oxidation potential which is not the same as disinfection capability. I believe you are right about this, though there is some correlation since the primary oxidizer in pool waters is chlorine (HOCl) which dominates the ORP reading. So in some sense, ORP acts as a proxy for HOCl. You are right, however, that it also has other pH dependencies and the actual reactions that are being measured appear to be close to 1 electron instead of the 2 one would expect with HOCl oxidation. I've had numerous discussions about this with several ORP sensor manufacturers which led me down the path towards comparing calculated ppm HOCl against the Oregon Commercial Spas study where I found that calculated (not even real-time) HOCl concentration was at least as good if not slightly better than real-time ORP (with one exception at low chlorine and zero CYA that was very, very strange).

I plan to start two new threads in the China Shop. One will be non-technical and will be focussed on getting more real-world information from users who are battling algae (maybe some will even be willing to try some experiments) -- perhaps Ben will move this out of the China Shop, but I'll leave that up to him. The other new thread will be technical and will address the issues I described above regarding ppm HOCl and ORP, giving you graphs, spreadsheets, etc.

Richard

[waterbear]

Evan (waterbear),

Thanks for the info on chloramines and their use in killing algae. I did read something about this in some non-scientific articles, but couldn't find good data on algae kill levels (for different algae types) for either chlorine (HOCl) or chloramines (NH2Cl) except for an EPA report that essentially said that 0.1 ppm chlorine (in sea water, so chloramines certainly were formed) killed most marine plankton. On the "Save Swimming with Elevated Chlorine" forum you mentioned that there were studies showing the relationship of ORP to different types of algae that grew in that environment -- I would appreciate links to those studies or a summary of results and whether there was ammonia present (so that chloramines would have formed), what the pH was, etc. I can roughly translate ORP to ppm HOCl at least to get an idea, both for maintenance and shocking.

The studies I cited come from various books and articles from the 70's when ORP controllers for marine aquarims were being first employed freqently with ozone and foam fractionalization (protien skimmers). I would not know where to begin looking today! (I experimented back then, found it viable, and just continued to use the procedures. Today they are pretty much standard practices in the hobby) As far as whether ammonia is present or not...ammonia is one of the biggest problems in marine or frehwater aquariums since the waste products of the livestock are nitrogeneous compounds. This is the reason biological filtration is used to convert ammonia first to nitrites and then to nitrates which are much less toxic. The buildup of nitrates is still problematic in reef tanks so ozne and foam fractionalization is used to reduce the initial loading of ammonia and then anerobic denitrification is used to reduce the remaining nitrates formed by aerobic nitrification (along with dilution). Also green algae is used to consume the nitrates and then harvested and removed from the tank to further reduce nitrate levels. If I am not mistaken the 450 mv reading of a 'healty tank' comes from the ability of the tank to oxidize the ammonia that is generated and it has a direct bearing on the type of algae that can grow. Foam fractionalization and ozone both will raise the mv reading in a tank and both lower the amount of ammonia present in the water. I have found from my own experiments that the type of lighting in the tank also has a bearing on the ORP readings...Actinic (440 angstom peak but quite a bit of the UVA spectrum) and metal halide (strong UVA/UVB component) tend to produce a higher mv reading than the same tank with daylight or wide spectrum lighing. I don't know of any studies that have been done on this but there might be. I attribute it to the UVA/UVB components of the lighting destroying the ammonia and related compounds in much the way sunlight would and therefore raising the redox potential of the water system. This is supposition on my part and the actual mechanism might be completely different.

It is interecting that CYA is a nitrogeneous compound and it is known to lower ORP readings in pool (as does combined chloramines). I am not really sure what the correlation between the level of nitrogen compounds and the ORP reading really means but it poses a lot of questions to me concerning actual sanitation vs. oxidation potential. A marine aquarium is NOT a sterile enviroment (although attempts have been make with sterile systems using UV and micron filtration with varying degrees of success) yet oxidative processes are necessary for the health of the system.

You also commented on the other forum (if I should respond there instead, let me know) about the use of ORP sensors and how these measure oxidation potential which is not the same as disinfection capability. I believe you are right about this, though there is some correlation since the primary oxidizer in pool waters is chlorine (HOCl) which dominates the ORP reading. So in some sense, ORP acts as a proxy for HOCl. You are right, however, that it also has other pH dependencies and the actual reactions that are being measured appear to be close to 1 electron instead of the 2 one would expect with HOCl oxidation. I've had numerous discussions about this with several ORP sensor manufacturers which led me down the path towards comparing calculated ppm HOCl against the Oregon Commercial Spas study where I found that calculated (not even real-time) HOCl concentration was at least as good if not slightly better than real-time ORP (with one exception at low chlorine and zero CYA that was very, very strange).

I plan to start two new threads in the China Shop. One will be non-technical and will be focussed on getting more real-world information from users who are battling algae (maybe some will even be willing to try some experiments) -- perhaps Ben will move this out of the China Shop, but I'll leave that up to him. The other new thread will be technical and will address the issues I described above regarding ppm HOCl and ORP, giving you graphs, spreadsheets, etc.

Richard
I look forward to your threads. I have a strong chemisty background and previous (a very long time ago!) research laboratory experience but am not a chemist and have been a serious marine aquarium hobbiest for over 30 years now. I hope that I can add something to your threads with my limited understanding of the concepts involved (although my understanding probably excedes that of the average non-technical person).

[chem geek]

I look forward to your threads. I have a strong chemisty background and previous (a very long time ago!) research laboratory experience but am not a chemist and have been a serious marine aquarium hobbiest for over 30 years now. I hope that I can add something to your threads with my limited understanding of the concepts involved (although my understanding probably excedes that of the average non-technical person).
You had mentioned various ORP levels that inhibited algae and all of these were quite low relative to the 650 mV level for sanitation. Maybe the level of HOCl to inhibit algae is below that for sanitation and it is only after algae is established (and forms a biofilm) that chlorine is not effective (except at "shock" concentrations)??? Or perhaps the lower ORP levels reflect monochloramine and that virtually no HOCl is present.

I have read that monochloramine is more effective against established algae since it reacts more slowly (weakly) than HOCl so it doesn't get "used up" by the biofilm layer and is therefore able to penetrate more deeply. If you have any way of figuring out what it takes to suppress algae and to kill algae, please let me know. We know from the experience on this forum that large amounts of chlorine will kill algae, but I'd like to quantify this further in light of our knowledge of HOCl concentration.

I've posted the technical thread in the China Shop called "Pool Water Chemistry". After I get that stable, I'll post another non-technical thread to ask for real-world algae experience.

Richard

[waterbear]

You had mentioned various ORP levels that inhibited algae and all of these were quite low relative to the 650 mV level for sanitation. Maybe the level of HOCl to inhibit algae is below that for sanitation and it is only after algae is established (and forms a biofilm) that chlorine is not effective (except at "shock" concentrations)??? Or perhaps the lower ORP levels reflect monochloramine and that virtually no HOCl is present.
My understanding is that the 650 mv is an arbitrary selection and have not been able to find anything that explains why this 'magic number' is the level at which sanitation occurs. It is interesting that in a 2005 CPO training handbook that I have seen it talks about 850 mv as being the level of adequite sanitation.
I have read that monochloramine is more effective against established algae since it reacts more slowly (weakly) than HOCl so it doesn't get "used up" by the biofilm layer and is therefore able to penetrate more deeply.
My understanding is that the algae will actually consume this as a food source as they consume other nitrogeneous compounds, hence the greater effectiveness.
If you have any way of figuring out what it takes to suppress algae and to kill algae, please let me know. We know from the experience on this forum that large amounts of chlorine will kill algae, but I'd like to quantify this further in light of our knowledge of HOCl concentration.

I've posted the technical thread in the China Shop called "Pool Water Chemistry". After I get that stable, I'll post another non-technical thread to ask for real-world algae experience.

Richard
Hope this is helpful.

[chem geek]

My understanding is that the 650 mv is an arbitrary selection and have not been able to find anything that explains why this 'magic number' is the level at which sanitation occurs. It is interesting that in a 2005 CPO training handbook that I have seen it talks about 850 mv as being the level of adequite sanitation.
Take a look at page 5 of the following link:

http://www.sbcontrol.com/ppmorp.pdf

The "Commercial Spas Study, Portland, Oregon" shows how the 650 mV ORP cutoff is reasonable for sanitation -- at least for the types of bugs found in those particular spas. There are clearly some bugs that require much higher concentrations of chlorine to get killed, but most bugs die below the 650 mV llevel. On the other hand, I found that the concentration of HOCl was at least as good if not a little better than ORP. I will put this information into the "Pool Water Chemistry" thread so you can see it.

You may also be interested in the following link that gives CT (C for concentration in ppm chlorine and T for time in minutes) values for various pathogens, though the focus is mostly on the ones that are hard to kill (for water treatment). The "easy" bugs (those easier than E. Coli) are not listed. Note that kill time is shortened at higher temperatures and the temps given are rather low.

http://www.who.int/water_sanitation_health/dwq/en/watreatpath3.pdf
http://anrcatalog.ucdavis.edu/pdf/8149.pdf

On the other hand, bacterial biofilms may require much more chlorine than is ever found in pools, even with shocking without CYA:

http://www.edstrom.com/Resources.cfm?doc_id=145


My understanding is that the algae will actually consume this as a food source as they consume other nitrogeneous compounds, hence the greater effectiveness.
I see you said that in your earlier post. Sorry I missed that the first time. If we try to use monochloramines for killing algae, then that will be a tricky combination of adding chlorine and ammonia. If CYA is present, then after the algae is killed, it will be virtually impossible to shock to breakpoint to get rid of the monochloramine, though it's possible a non-chlorine shock could do the trick.

Thanks for your comments. They are helpful.

Richard

[waterbear]

I see you said that in your earlier post. Sorry I missed that the first time. If we try to use monochloramines for killing algae, then that will be a tricky combination of adding chlorine and ammonia. If CYA is present, then after the algae is killed, it will be virtually impossible to shock to breakpoint to get rid of the monochloramine, though it's possible a non-chlorine shock could do the trick.

Thanks for your comments. They are helpful.

Richard Actually, the use of monochloramines for killing algae is not a new practice. Many 'old time' pool guys would add per 20000 gal water 1 gal anhydrous ammonia and 8 gallons of 12..5% hypochloruous acid (50 ppm) to form monochloramines in the water. Filtration is shut off for 24 hours and then an additional 8 gallons of chlorine is added and filtration turned on to destroy the chloramines. This is similar to the use of 'chlorine enhancers' that are based on inorganic ammonia compounds and are used to kill algae. They do create a huge chlorine demand in their aftermath. Perhaps PoolDoc (Ben) would have some more insight into this older practice.

Also, my understanding of MPS is that it will not break down chloramines....this info comes right off the DuPont Oxone website. They work by having a residual in the water to oxidize organics before choramines can form. This is a quote
" Does Oxone® reduce chloramines?
Products containing Oxone® prevent chloramines from forming by oxidizing contaminants. Regular oxidizing with Oxone® keeps contaminant levels to a minimum, so the water remains clear and sparkling, allowing you to enjoy longer periods of uninterrupted swim time. And because Oxone® is chlorine-free, you don't have to worry about high chlorine levels; chloramines; unpleasant odors; or burning, irritated eyes."
Here is the link
http://www.dupont.com/oxone/faq.html#a4

I can understand the benifits of MPS with an indoor pool but the caveat seems to be that a residual of MPS is required in the water at all times for them to be effective in the prevention of the formation of chloramines. I see no real advantage to their use in outdoor pools.

The only other non chlorine shock I am aware of is sodium percarbonate, which from my understanding, is no longer being used because of the effects it had on ORP controllers. It is still employed in limited use with conversion of biguinide to chlorine but I doubt it is really any better than chlorine for that purpose.

[chem geek]

Also, my understanding of MPS is that it will not break down chloramines....

I can understand the benifits of MPS with an indoor pool but the caveat seems to be that a residual of MPS is required in the water at all times for them to be effective in the prevention of the formation of chloramines. I see no real advantage to their use in outdoor pools.

Yikes! I had no idea that MPS didn't oxidize monochloramine, but the Dupont literature certainly implies that MPS only prevents their formation. Ben told me that supercholorination to achieve breakpoint almost never works, especially for indoor pools with poor air circulation. He speculated that sunlight breaks down monochloramines in outdoor pools and I've read literature that suggests the same thing.

So this begs the question of how do you get rid of monochloramines? If a pool has CYA in it, then you need a heck of a lot of chlorine to properly shock it. Originally I was thinking that a small amount of CYA for indoor pools was a good idea to reduce effective chlorine concentrations to minimize exposure to bathers (and their swimsuits), but that would make superchlorination even more difficult. A real catch-22. Why wouldn't you use a constant level of MPS to prevent monochloramine formation? Is this not necessary in outdoor pools due to the breakdown from sunlight?

(NOTE: I have contacted Dupont to ask them if their MSP product, Oxone, will oxidize monochloramine in which case it could be used as a shock and not just as a chloramine preventative. I will let you know their response, if any.)

[chem geek]

Okay, I got a response from DuPont on Oxone, but I'm not sure how to be diplomatic about this since I don't want to burn any bridges. I suppose I will paraphrase the jist of the response.

The response I got was essentially that combined chlorines are always being formed as people go into the pool, swim, and prespire. There is no technology on the market today that gets rid of persistent combined chlorines [I suppose that's by definition of "persistent"]. Using chlorine as a shock will oxidize some contaminants, but it will also lead to an increase in combined chlorine [again, I suppose he's talking about the "persistent" variety of combined chlorines since the shocking would probably dispose of the "easier" combined chlorines]. Since Oxone [MPS] is non-chlorine, it cannot form chloramines [very true]. Also, by eliminating periodic high chlorine doses, one reduces chloramine formation [here it sounds like he's talking again about the more complex organic chloramines, not the simple ammonia-based monochloramine]. In pool water samples, they have seen destruction of the "monochloramine" component of combined chlorine by Oxone. This "monochloramine" component is almost certainly not NH2Cl, but a chloramine species which mimics NH2Cl in the DPD test [again it sounds like this is an organic chloramine]. In fact, NH2Cl cannot exist in actual pool water where there is always a free chlorine residual [I believe he is talking about the breakpoint reaction of chlorine preventing NH2Cl from remaining].

I then wrote back with more details and questions (such as the breakdown of monochloramines by sunlight, the impact of CYA on low HOCl and low breakpoint rates, the differences of outdoor and indoor pools, etc.), but haven't heard back and may not. So what's the bottom line? Using MPS in a preventative dosage will likely prevent chloramines of any type from forming so shocking with chlorine will not be necessary and may not work completely anyway (at least for that purpose -- it would still be needed for killing algae blooms but they shouldn't happen at all if chlorine levels are maintained).

Since I have not seen any significant reports from users of this forum on battling Combined Chlorine when using BBB or other methods that do not use non-chlorine shock, it would appear that the use of MPS may not be necessary in residential outdoor pools (commercial pools with high bather loads might be different). On the other hand, there are frequent reports of problems with indoor pools so perhaps MPS would be quite useful in maintenance doses in that environment. What we don't know for sure is what exactly is the difference between these two environments that is the root cause of the CC difference that makes outdoor pools much easier to manage. Is it the sunlight (UV) breakdown of choramines? Is it the greater air circulation? Is it the use of CYA (doubtful)?

[EDIT] For an alternative point of view based on experience, read Ben's tip (http://www.poolsolutions.com/gd/chem_never.html). I'm giving the DuPont Oxone a little more credit for possible benefit in indoor pools. I am also one with the heretical idea of using a small amount of CYA (10 ppm or less) in indoor pools to lower the effective chlorine concentration to reduce exposure to clothing and people. However, using CYA means that superchlorinating is much harder, but if the CYA amount is small enough, then you can fairly easily overwhelm the CYA and get lots of pure chlorine in your pool during shocking (e.g. 15-20 ppm chlorine), but that's a topic for another thread (someday)! [END-EDIT]

Richard