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Hot Tubs And The Spread Of Diseases?


trucker11

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As a new tub owner, I was just watching the news about the super bug that is hitting the northeast, and I assume elsewhere. This is a staph infection that there is no vaccine for. Anyway, I was wondering since I have two teenagers with all their friends coming over to use the hot tub, plus our own friends, is there any more particular steps that should be taken beside shocking and chlorinating, which of course I do.

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According to the table on this CDC web page, the Staphylococcus aureus bacteria which is the one you are talking about has a CT value of 0.4 which is relatively small and means it is relatively easy to kill with chlorine. The concentration of disinfecting chlorine depends on the Cyanuric Acid (CYA) level so if you were to use Dichlor as your source of chlorine, then the CYA level may get high, but even with a CYA of 100 ppm and a Free Chlorine (FC) level of just 1 ppm, this bug would have an effective 100% reduction in less than 40 minutes and it could be a lot less since the table indicates a 100% reduction making it impossible to precisely calculate. If you were to maintain the spa with my recommendation of 4 ppm FC with 20 ppm CYA, then this bug would get killed in less than 2 minutes.

The bottom line is that you should not worry about this super bug somehow growing in your spa.

Richard

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According to the table on this CDC web page, the Staphylococcus aureus bacteria which is the one you are talking about has a CT value of 0.4 which is relatively small and means it is relatively easy to kill with chlorine. The concentration of disinfecting chlorine depends on the Cyanuric Acid (CYA) level so if you were to use Dichlor as your source of chlorine, then the CYA level may get high, but even with a CYA of 100 ppm and a Free Chlorine (FC) level of just 1 ppm, this bug would have an effective 100% reduction in less than 40 minutes and it could be a lot less since the table indicates a 100% reduction making it impossible to precisely calculate. If you were to maintain the spa with my recommendation of 4 ppm FC with 20 ppm CYA, then this bug would get killed in less than 2 minutes.

The bottom line is that you should not worry about this super bug somehow growing in your spa.

Richard

Thank you for your prompt and very detailed answer. I keep my FC between 3 and 5 so will not worry about this any more.

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  • 4 weeks later...

It is also important to instruct anyone using the spa to not get in if they have open wounds or skin infections. Not only to protect the other users, but people with open wounds will be more suseptable to infections themselves. Remember, hot tubs are NEVER sterile!

Also, all users should shower just before entering the hot tub.

Be sure to check the chlorine and pH just prior to use, and after use, and dose appropriately. Your son is old enough to train him how to do this if you are not home when he and his friends use the spa. If your hot tub is allowed to drop below 1ppm for any length of time consider draining the water and fully scrubbing the spa. Once biofilms are allowed to build up in the pipes, they are resistant to chlorine. http://www.apsp.org/APSPRWQE-news/recreational.html

Don't forget to wipe down the sides of the hot tub that are not in contact with the chlorine.

I am not a pool and spa expert, but I am a registered nurse who contracted Legionnaires disease http://www.isrm.co.uk/recreation/documents...pp32-34_000.pdf from a California hotel hot tub in 2001. I have been researching the issues of hot tub infections for the last six years.

Stacy Intille RN

According to the table on this CDC web page, the Staphylococcus aureus bacteria which is the one you are talking about has a CT value of 0.4 which is relatively small and means it is relatively easy to kill with chlorine. The concentration of disinfecting chlorine depends on the Cyanuric Acid (CYA) level so if you were to use Dichlor as your source of chlorine, then the CYA level may get high, but even with a CYA of 100 ppm and a Free Chlorine (FC) level of just 1 ppm, this bug would have an effective 100% reduction in less than 40 minutes and it could be a lot less since the table indicates a 100% reduction making it impossible to precisely calculate. If you were to maintain the spa with my recommendation of 4 ppm FC with 20 ppm CYA, then this bug would get killed in less than 2 minutes.

The bottom line is that you should not worry about this super bug somehow growing in your spa.

Richard

Thank you for your prompt and very detailed answer. I keep my FC between 3 and 5 so will not worry about this any more.

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Stacy,

Thank you for that information and link and I'm sorry you contracted Legionnaires disease. There was no mention of the type of chlorine source used in the hot tubs and in my view that makes a big difference in terms of the level of disinfection. Cyanuric Acid (CYA) is known to reduce chlorine's effectiveness and some of the regimens used for disinfection in hot tubs are to use Dichlor only. For every 1 ppm FC added by Dichlor, it also adds 0.9 ppm to CYA. That builds up CYA so the chlorine becomes less and less effective. Since the bacteria that causes hot tub itch, Pseudomonas aeruginosa, is more resistant to chlorine, I recommend using Dichlor for one week or two to get to around 20 ppm CYA or so and then switch to unscented bleach with a 4 ppm FC target. This should kill this bacteria (over time) that has a 4-log 99.99% CT value of 30-50 (Legionella pneumophila has a 2-log 99% CT value of around 19 so is similar).

The Department of Health in Pennsylvania recommends not using CYA or stabilized chlorine in hot tubs or spas or for indoor pools (see this link), but I think that is too extreme and results in overdosing with disinfecting chlorine -- some CYA is good, too little or too much is not. See this link for more technical information I've posted about this subject. Also note this link that shows that Potassium Monopersulfate (MPS) non-chlorine shock when combined with a catalyst such as Copper sulfonated phthalocyanine (CuPC) can break down biofilms. So a regular regimen using chlorine (watching the FC/CYA ratio) and MPS should be effective and with the use of metal ions may be even more effective if regular sanitation has been lax (though copper or silver ions may not catalyze MPS the same way by themselves). Though shocking with a higher level of chlorine can help remove biofilms, with CYA in the water (even at my recommended amounts) it is hard to shock at high enough of a level. Instead, there are stronger oxidizers such as sodium percarbonate and sodium chlorite (which when added to chlorinated water produces chlorine dioxide -- see this link) that very effectively destroy biofilms, but both of these consume chlorine so can't be used on a regular basis. However, prevention is best and biofilms won't form if chlorine levels are maintained, so I agree with your advice that the chlorine level should never be allowed to drop too low.

I'd love to get more information that you have on hot tubs, disinfectants and pathogens. Please post here or PM me (I can give you an E-mail address).

Richard

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