Hot Tub Forum
Original => Hot Tub Forum => Topic started by: Vermonter on July 31, 2006, 09:32:15 am
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Continued from Part 2:
Why don't hot tub manufacturers make powerful enough units? I'll admit, it's been a couple of years since I've really looked into this and it is possible that someone has. But the age-old problem is that since the transfer process of the ozone from the gas (bubble) phase to the aqueous (dissolved) phase is so poor that to get any ozone in the water you would generate so much off-gas that the units would fail federal limits. I have read of some "off-gas destruct" units that would theoretically take care of some of this - but I have yet to see any manufacture of tub or ozonator publish defensible, empirically generated data on dissolved ozone concentrations in tubs. A couple of years ago, my personal communication with a very, very large tub manufacturer and the largest manufacturer of ozone generators for factory installed units (in hot tubs) confirmed that it is "unlikely" to be able to achieve and measurable ozone level in the hot tub water itself. That may have changed and I would welcome any input on that.
But, keep in mind, even if you get a residual in the contact chamber and, after satisfying the oxidative demand, you get some antimicrobial (killing) action going on, since you don't have anything close to "plug-flow" in a tub, there is no way that the residual will be able to be maintained in the main tub or that all the contents of the main tub will be exposed to the contact chamber before being "recontaminated" (keep in mind the half-life and temperature related problems).
Bottom Line:
There is much, much more I could write on ozone - but my goal was to give basic information on what ozone is, how it works, how it is applied to hot tubs and to hopefully give a basic understanding of what it would take for ozone to work as a sanitizer in hot tubs.
Ozone is widely used in the drinking water, food, semiconductor and other industries as a sanitizer / disinfectant. It is a popular option for many hot tubs and, in my opinion, functions as an oxidizer and, as a result, may slightly reduce the need for your normal oxidizer / sanitizer. I have yet to see any data to support any claim that ozone can function as a stand-alone sanitizer in hot tubs or, for that matter, that it can exert any "killing" effect on microbes in hot tubs.
Do I have it on my hot tub? Yes! Will I keep it? Yes! Is there any scientific reason for that? No - at least not based on any numbers I have been able to generate or that I have seen in the literature! But I enjoy watching the bubbles!
Best,
Vermonter
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But I enjoy watching the bubbles!
BINGO!!!
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Hey V-man, long time, hope things are well with you.
Couple questions to "get this party started". I think I understand you to say that until everything in the water is oxidized, the ozone wont begin to sanitize. Correct?
2. With regards to "contact chambers"... They all pretty much seem to consist of a long piece of horizontal pipe (as opposed to a true mixing chamber). Aren't the little bubbles of ozone going to rise rather quickly to the TOP of the pipe, combining into one big ole bubble, thereby no longer being able to be absorbed into the water (and the slower the water is moving, i.e. circ pump, the less turbidity there will be allowing for a faster rise of the bubbles)?
Hottubman made an interesting comment in another thread, suspecting that the real purpose of a contact chamber was to give the ozone enough time to revert back to 02 thereby reducing off-gassing.
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I am not sure if other companies do this, but on Sundance spas there is an actual "chamber" that breaks the bubbles down as they are passing through.
Vermonter, very nice posts.
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2. With regards to "contact chambers"... They all pretty much seem to consist of a long piece of horizontal pipe (as opposed to a true mixing chamber). Aren't the little bubbles of ozone going to rise rather quickly to the TOP of the pipe, combining into one big ole bubble, thereby no longer being able to be absorbed into the water (and the slower the water is moving, i.e. circ pump, the less turbidity there will be allowing for a faster rise of the bubbles)?
HS uses spa flex - which has a slight spiral built in. I know they try to keep the tubing absolutey level as it makes it's rounds to avoid the bubbles clumping and getting noisey as well, but I guess that's what we would call a "pipe dream" - pun intended.
The spiral induces a swirling motion which seems to keep the bubbles small and mixes them. I have not seen this in action with a pipe camera or anything, so I can't verify that it is doing a perfect job, and the spiral is very minor, nothing more than all spa flex has. But the bubbles emerging from the botton fitting are still pretty small - especially on the newer tubs - so I have to think they are staying well suspended during transit through the chamber.
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"I know they try to keep the tubing absolutey level as it makes it's rounds to avoid the bubbles clumping and getting noisey"
You said it right there. Little tiny bubbles only make a hissing noise. Gergling is only from large bubbles.
I also find it rather unlikely that the natural twist of flex PVC will cause anough agitation to keep the tiny bubble from rising, especially with a small circ pump moving little water.
Real life story... About 15 years ago we installed a hot tub and the equipment, which included an ozonator (BIG dual 28" UV lamps), a mazzie injector and mixing chamber was about 60' away. The piping ran flat and level on top of a concrete wall footing, straight from the equipment to the tub. You could hear the big fat bubbles inside the pipe not very far after the injector/mixer.
It took a bit of playing with the plumbing and orientation of the jet, but we finally got it so the jet was "rearrosoling" the big bubbles back into tiny bubbles as the water shot out into the tub.
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Hey V-man, long time, hope things are well with you.
Hi Doc - yes, long-time. Things are going well - I'll try to catch up with you by email!
Couple questions to "get this party started". I think I understand you to say that until everything in the water is oxidized, the ozone wont begin to sanitize. Correct?
That is correct - to the best of my knowledge.
2. With regards to "contact chambers"... They all pretty much seem to consist of a long piece of horizontal pipe (as opposed to a true mixing chamber). Aren't the little bubbles of ozone going to rise rather quickly to the TOP of the pipe, combining into one big ole bubble, thereby no longer being able to be absorbed into the water (and the slower the water is moving, i.e. circ pump, the less turbidity there will be allowing for a faster rise of the bubbles)?
I think the flow, even at a HS 4 - 6 gpm in the circulating pump / ozone injection line, is fast enough to prevent many from "clumping" on the top of the pipe. An improvement, in my opinion, would be to install a Kenics (or equivalent) static mixer immediately downstream (allowing for manufacturer's recommendations for straight pipe length in and out of the mixer. This allows highly efficient mixing of two phases (e.g. gas and water) and would help the mass transfer process.
A few years back, I tried modifying my "contactor" on my HS and added a coil of approximately 75 feet of 3/4 " I.D. tubing figuring that this would give an "ultimate" (well, not quite) contact chamber and ozone transfer to the dissolved state. Unfortunately, the back pressure resulting from the combination dropped the flow rate below the minimum for the Mazzei injector installed in my Grandee so suction / injection was no longer occurring. I haven't gone back to try some half-way measure.
Hottubman made an interesting comment in another thread, suspecting that the real purpose of a contact chamber was to give the ozone enough time to revert back to 02 thereby reducing off-gassing.
That is an interesting thought.
Two immediate thoughts:
First, the logic of that happening would assume that, ideally, the half-life is less than or equal to the residence time in the contact chamber. I don't recall what the ID is on the tubing coming out of my HS Mazzei injector (I think it is smaller than the 3/4" I used as mentioned above). If it is 1/2", then the volume per linear foot is about 0.04 liters or about 0.1 gallons. In 10 feet, you would therefore have about 1 gallon. If you are flowing at 4 - 6 gpm, then the residence time in that section would be 10 - 15 seconds - so I'm not sure that you would see much benefit.
Second, since the vast majority of ozone is still going to be contained in the non-dissolved bubbles (probably about 90% but I don't know the exact %) being carried the length of the contactor, and since the half-life of ozone in the gaseous state (i.e. what is in the bubbles) is much longer than in the dissolved state in "unpure" tub water, I think the majority of the ozone would still be carried out into the tub (undissolved) in the bubble form and rise to the surface only to then release the ozone / air mix.
I hope to get back to your board again...
Vermonter
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hmmm...my apologies...
I seem to be having a problem with this "reply" feature. Sorry about that - some of my response is in the blue box and some not!
Vermonter
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hmmm...my apologies...
I seem to be having a problem with this "reply" feature. Sorry about that - some of my response is in the blue box and some not!
Vermonter
The nice thing is you can go back and modify the post.
If you want to show his quote, answer and then show another quote and answer you'll have to arrange the quote brackets (beginning and ending) around each one of his quotes.
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Vermonter
Isn't te real idea behind adding ozone to a tub is to get the "bugs" that are resistant to chlorine. Since chlorine is the principal sanitizer, ozone should only have to target those resistant "bugs". I know that it will effect everything in its path but since chlorine has no effect on some bugs, isn't that all your asking ozone to do?
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Isn't te real idea behind adding ozone to a tub is to get the "bugs" that are resistant to chlorine. Since chlorine is the principal sanitizer, ozone should only have to target those resistant "bugs". I know that it will effect everything in its path but since chlorine has no effect on some bugs, isn't that all your asking ozone to do?
Hi Northern Neighbor,
My personal answer to your question is "no". Given a proper dichlor regimen, there are no bacteria or viruses that I am aware of that would make it through chlorine treatment (applied correctly). Ozone, while more efficient in some respects than free chlorine, has to be present at some measurable levels for some period of time to be effective on even some of the simpler gram negative and gram positive bacteria. My testing, and my research, has not demonstrated to me that any hot tub / ozonator combination is able to produce and maintain a dissolved ozone residual in the main hot tub and, as a result, it cannot be relied on as a primary sanitizer in hot tubs (drinking water and other applications are different).
The only microbes that are classically viewed as chlorine resistant are some of the spore formers and mycobacteria, along with the protozoan Cryptosporidium. Even then, with proper pH and sufficient chlorine CT, they are able to be inactivated or killed.
If a dissolved ozone residual could reliable be produced and maintained in the main hot tub (so far, I have seen no peer-reviewed research to suggest that it can) then it could claim to be a primary sanitizer and would go a long way toward a much more "chemical free" treatment regiment than any of the more traditional approaches.
Vermonter
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Hi Northern Neighbor,
My personal answer to your question is "no". Given a proper dichlor regimen, there are no bacteria or viruses that I am aware of that would make it through chlorine treatment (applied correctly).
The only microbes that are classically viewed as chlorine resistant are some of the spore formers and mycobacteria, along with the protozoan Cryptosporidium. Even then, with proper pH and sufficient chlorine CT, they are able to be inactivated or killed.
This may be false info that I have been given, you have much more experience that I. The drinking water industry has started to use ozone for the treatment of cyrpto and giardia due to thier resistance to chlorine. I know the chances of either occuring in your hot tub are very slim, but if ozone can get them I,m happy it there.
Its fantastic to be able to "pick your brain" on this subject
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The drinking water industry has started to use ozone for the treatment of cyrpto and giardia due to thier resistance to chlorine. I know the chances of either occuring in your hot tub are very slim, but if ozone can get them I,m happy it there.
By Golly,
You are correct about Crypto's (and to a lesser extent, Giardia's) resistance to chlorine and that ozone works better. But, check out the CT requirements of ozone for Crypto (I can dig out a reference if you need) - and if ozone in hot tubs can't produce and maintain a measurable dissolved residual, then ozone's effectiveness doesn't apply (you HAVE to have a residual).
I have nothing against ozone - actually I think it is a great disinfectant. But, I do not like the implications or claims that manufacturers make that it functions as a sanitizer in hot tubs and then those same groups cannot produce solid test data supporting that claim.
Best,
Vermonter
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EXCELLENT INFORMATION !!!!
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Your right ozone and crypto CT is I believe 2.5
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ozone's effectiveness doesn't apply (you HAVE to have a residual).
But, I do not like the implications or claims that manufacturers make that it functions as a sanitizer in hot tubs and then those same groups cannot produce solid test data supporting that claim.
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Sorry now I messed up the quote thing,
Are you claiming that ozonators do not work in tubs or just that there is no info that they do?
Another question, since ozone does improve the water quality, can we not assume a short residual?
Sorry about the earlier post and run.
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In_Canada_eh,
Are you claiming that ozonators do not work in tubs or just that there is no info that they do?
Interesting question - sure you're not an attorney? I'll say (my opinion), "yes" to both questions. The reasons for "yes" are based on my own (admittedly, limited) testing, understanding of the use of ozone in aqueous systems and the lack of any published, defensible data from tub manufacturers or ozonator manufacturers (you would think they would publish confirming information on the effectiveness if they actually had it, wouldn't you?).
Another question, since ozone does improve the water quality, can we not assume a short residual?
As sort of mentioned in one of my earlier posts, I think that ozone can, and does, function as an oxidizer (especially it is 24/7) and, depending on the degree of tub usage, can certainly contribute to overall tub physicalchemical quality. It certainly won't hurt and I think it helps.
However, any residual present either has its oxidative demand totally quenched by the organic / inorganic contaminants in the tub water so the issue of a residual is a moot point or, if not, the residual is too low (my experience) to be measured by a highly sensitive, ozone specific measurement method.
Vermonter
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Wow! You are quite an asset to the board Vermonter...Thanks for the input!
I do have a couple of questions for you because it sounds like you know your stuff.
1. If ozone is an effective sanitizer and kills bacteria then being an airborne oxidizer what is to keep it from wiping out the good bacteria in our lungs? Considering the fact that most spas "dump" the ozone into the bather load while it is still active I would think that it could actually be a health risk?
To my knowledge the EPA regulates home air purifiers to the amount of ozone they put out and it's a whole lot less than spas. Why do they regulate that?
Here is an ugly scenario if this works like I think it does...in most spas ozone collects in the trapped air between the water and the cover, you open the cover and breath the ozone into your lungs depleting the stores of good bacteria that fights of disease. Then you get into the spa and sweat around a pint of fluid that breeds bad bacteria in the over 100 degree water and when you turn the jets on you make some of that airborne and breath it in causing respiratory issues.
I think that this is a problem with spas that has never been addressed
2. Second Question is more of a statement…. As everyone knows, we sell several brands of spas. Giving all of our wet models the same attention the difference in water quality in the D1 line is very noticeably better then the rest without added sanitizers. They don’t filter more, they don’t have a frog system but they stay really clean. It is my belief that this is because of the fact that they do more than 98% of the ozone in the plumbing and not the bather load keeping the ozone in contact with the water longer than just about any other manufacture.
Your input here would be greatly appreciated!!
BTW, here is a link to the EPA site talking about O3
http://www.epa.gov/iaq/pubs/ozonegen.html#table%201
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Wow! What an education! Not sure I understood it all (or really need to). But, i have a much better idea of why I absolutely need to add dichlor and not just depend on the Ozonoator and Nature 2 cartridge to do all the work in between my weekly shock (which is all the dealer told me would be required).
Tonight I started dichlor! Looking forward to the water staying clear all the time (once i've got the routine down pat) and also after reading about that the ozonator is not a magic bullet, I feel so much better that I will be effectively killing bacteria for real.
Thanks!
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Vermonter
Are you familiar with Wallace and Tiernan amperometric residual analyzers.
http://www.usfilter.com/en/Product+Lines/Wallace_and_Tiernan_Products/Wallace_and_Tiernan_Products/wallaceandtiernan_product_Depolox+3+Plus.htm
Its a massive link but they make a very good product.
I know that we can't ask a tub owner to have this installed but, I wonder if one of the ozone makers (Delzone or Jed) has ever used one. It may be the test that would or would not prove ozones use in tubs
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In_Canada_eh,
Interesting question - sure you're not an attorney? I'
Positive on that, I am very happy just being a toolmaker and mechanic
Once again Sir/Madame it is an honor to have you contributing to this forum
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1. If ozone is an effective sanitizer and kills bacteria then being an airborne oxidizer what is to keep it from wiping out the good bacteria in our lungs? Considering the fact that most spas "dump" the ozone into the bather load while it is still active I would think that it could actually be a health risk?
Hi stuart,
Tub manufacturers, and, I believe, ozonator manufacturers (for hot tubs), are required to have their units tested to national standards to ensure that the offgas production of a functioning unit does not exceed safety standards - at least if they want to be able to list their tubs as, I believe, UL (perhaps it is OSHA) approved. As I recall (it's been some time since I looked at this) the whole tub is placed ina 10'x10'x10' closed room and three ambient (gaseous / air) monitors are placed in the room. Again, as I recall, one is in the equipment cabinet, one in the area immediately above the tub and one somewhere else in the enclosure. The ozonator and tub are turned on and I believe that the test period (ozonator running continuously) is either 8 hours or 24 hours and none of the readings at any of the monitors / sensors can exceed the OSHA (?) established levels.
Your link also points out that if ambient ozone levels are at or below the established safety limits that no effective "killing" of microbes would occur. So, I am personally comfortable in not being concerned about ozone off-gas from a hot tub being high enough to do me any harm.
To my knowledge the EPA regulates home air purifiers to the amount of ozone they put out and it's a whole lot less than spas. Why do they regulate that?
Your link (and there are numerous other good authoritative links on this subject) points out the potential health effects of ozone at "unsafe" levels as being:
Potential risk of experiencing:
Decreases in lung function
Aggravation of asthma
Throat irritation and cough
Chest pain and shortness of breath
Inflammation of lung tissue
Higher susceptibility to respiratory infection
So, as with many other airborne chemicals, regulatory agencies have established both short-term and long-term maximum levels. This has been done with gaseous (airborne) ozone.
Here is an ugly scenario if this works like I think it does...in most spas ozone collects in the trapped air between the water and the cover, you open the cover and breath the ozone into your lungs depleting the stores of good bacteria that fights of disease. Then you get into the spa and sweat around a pint of fluid that breeds bad bacteria in the over 100 degree water and when you turn the jets on you make some of that airborne and breath it in causing respiratory issues.
This is pretty much covered above - tubs are designed so that they meet national health / safety standards with respect to their production of off-gas which would then become the airborne ozone you are referring to.
I think that this is a problem with spas that has never been addressed
2. Second Question is more of a statement�. As everyone knows, we sell several brands of spas. Giving all of our wet models the same attention the difference in water quality in the D1 line is very noticeably better then the rest without added sanitizers. They don�t filter more, they don�t have a frog system but they stay really clean. It is my belief that this is because of the fact that they do more than 98% of the ozone in the plumbing and not the bather load keeping the ozone in contact with the water longer than just about any other manufacture.
As pointed out in some of my earlier posts in this and related threads, while I strongly do NOT believe that there iis any defensible data to indicate that ozonators on hot tubs are effective in controlling microbes, I do believe that ozone (are D1's 24/7? for ozone) can and will result in physical/ chemical benefits to the hot tub water. That opinion is based not only an understanding of what ozone is and how it works, but also on the testimony of you and many others who state emphatically that they see an improved water quality when ozonators are used. Would all ozonators cause an improvement? Probably not - this gets into design considerations such as ozonator output, water temp, contact chamber design, amount of mixing of the bubbles with the water, etc.
Best,
Vermonter
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This is pretty much covered above - tubs are designed so that they meet national health / safety standards with respect to their production of off-gas which would then become the airborne ozone you are referring to.
I think that this is a problem with spas that has never been addressed
Lets not kid ourselves....Most spa manufactures DO NOT care if they meet national health / safety standards nor is there any spa police out there checking. I think you would be surprised at how many of the over 200 manufactures have never been tested and I would bet less then 20 of them actually comply. Some claim UL because the equipment pack is UL but the spa is not. I will just about guarantee that if you buy a spa off the Internet it will not have met many of these standards.
Besides, UL really has not addressed this well, neither has ETL and I personally believe it is a bigger problem than we think. It's my opinion that many people get a cough or sinus infection after setting in the spa the night before and blame it on weather or something else when it was the spa all along.
I love what I do and truly appreciate the benefits of what our products do for customers and their families but really wish we would get some safety regulations that are realistic and enforceable.
...and your correct, this and other things have never been addressed.
BTW, to my knowledge ozone manufactures are not held to a standard of how much ozone the put into a spa.
Somewhere in my Metrology days I remember a home test you could do to test ozone...I will try to look it up and post it.
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Wow! What an education! Not sure I understood it all (or really need to). But, i have a much better idea of why I absolutely need to add dichlor and not just depend on the Ozonoator and Nature 2 cartridge to do all the work in between my weekly shock (which is all the dealer told me would be required).
Thanks!
This is exactly what I mentioned earlier along with Steve....some dealers want to try and convince someone they have almost magic water in their spas and it will be sanitizer free....simply untrue but with the right and regular care it can be very simple and safe....
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This is exactly what I mentioned earlier along with Steve....some dealers want to try and convince someone they have almost magic water in their spas and it will be sanitizer free....simply untrue but with the right and regular care it can be very simple and safe....
I agree - 100%!
Vermonter
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Your right ozone and crypto CT is I believe 2.5
That value of 2.5 may actually be low, depending on what the % disinfection goal is. The January 5, 2006 Federal Register (40 CFR Parts 9, 141 and 142 dealing with the Final LT2 rule whic is aimed at Cryptosporidium in drinking water) lists, in Tble IV.D-3, CT values for Ozone at various water temps. For 30'C (well below hot tub temps), they give a CT of 4.7 for a 3-log (99.9%) reduction in Crypto.
But, whether it is 2.5 or 4.7 or some other number, let's look at what that means in a hot tub:
If, for the sake of discussion, we assume that you don't have an ozone residual of any level being able to be produced and maintained in the hot tub itself, you are forced to rely on the dissolved ozone residual that would be present in the contact chamber. Let's say that you have a residence time of 1 minute (this is likely longer than most, if not all tubs, actually have), this means that for the discrete parcel of water that you have injected ozone into, ithat parcel of water would stay in the contact chamber for 1 full minute.
Since I believe some of the slower circulation / injection tubing pumps are pumping at 4 - 6 gpm (as in HotSpring), then the volume of water in the tubing would have to b3 4 - 6 gallons to get that 1 minute of contact time. This isn't likely to be the case (volume would be a fraction of that within the 10 feet or so of tubing), but, even if it was the case, you would then have to have an ozonator capble of putting 4.7 mg/L of dissolved ozone into the water AND assume no decay or half-life drop for one full minute.
No testing of mine and no reports that I have EVER seen have been able to claim a dissolved ozone residual of any level much less up in the range of 4.7 mg/L. And, even if you could have that in the contact chamber, to be "safe" you would want something close to that in the hot tub itself since you are not able to be ensured that every parcel of water in the tub goes through the contact chamber on a regular basis.
Luckily, the chances of Crypto being present in hot tubs should be relatively small and, unless you ingest them, you won't have a problem (i.e. don't drink you hot tub water!!).
Vermonter