I BBBed my hot tub , but it won't stay

[waterbear]

IF you use the hot tub during the day or have it uncovered for any reason during the day I would put in CYA. The most commen form of chlorine for hot tubs is dichlor. This is what is usually recommened by hot tub dealers when you go on a chlorine system. Dichlor is stabilized chlorine so it will add cya to the water. My hot tub is chlorinated by my SWG and has a CYA level of 70 ppm. If you maintain a steady FC level in the tub like you do in your pool there should be no problems! It's when people ignore the tub and only chlorinate it when they use it that it becomes a bacterial stew!

[EricF]

Thanks Evan,

I agree that maintaining steady, proper chlorine levels is THE MOST IMPORTANT thing, but I am still leery of the reports various health departments and the CDC linking pseudomonas infections and cyanuric acid use in spas.

This quote from the Pennsylvania Dept. of Health in my previously cited source is telling.

"Should cyanuric acid be used in hot tubs or spas? – At even moderate levels of cyanuric acid, the amount of time it takes chlorine to kill pseudomonas aeruginosa (the bacteria that causes “hot tub itch”) can be as much as a hundred times as long as in a hot tub or spa without cyanuric acid. For this reason, the Pennsylvania Department of Health does not recommend the use of cyanuric acid or stabilized chlorine in any hot tubs or spas."

Also see this link:

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4948a2.htm

I admit the outbreak occurred in these PUBLIC spas primarily due to lack of chlorine, but they still warn about an association with CYA. I admit, in private spas this may not apply at all. But having seen the effects pseudomonas can have on patients, it is something I am very sensitive to.

I use a SWCG in my pool, but have a standalone hot tub in which I use BBB. In my case, adding a small amount of bleach every other day works fine when it is covered during the day to keep my levels above 4ppm without CYA. If it is going to be used during the day (which I admit, is rarely), I double or triple the dose, but still it is just a few ounces of bleach in a 600 gallon spa to maintain adequate levels.

Any thoughts? Just trying to stimulate discussion.

Thanks,

EricF

[keithw]

I added some stabilized shock yesterday that really moved the chlorine level up and it held overnight so I guess I am fine now. But if CYA is of no benefit then I will not be adding any more. I'll just chlorinate w/bleach and see if it holds. Perhaps I just didn't get it up high enough or it was still working out bits of Baqua-crap. Yesterday I did notice some crap on the floor and seats and vacuumed it out. Looked kinda like sand but could have been some other sludge. I really only use my tub at night an usually only keep 1/2 of the cover off so I don't get much if any sun exposure.

Thanks for all the info.

[RavenNS]

I thought that CDC article was very interesting. However, I did not see any link or possible conclusion that suggests that cya is bad in this report.
In both cases listed in the report, the bacterial problems were caused by malfunctioning chlorine injection feeders... lack of disinfectant caused bacterial growth.
Poor monitoring increased potential for fatal results.

what it does say about Cya is:
" cyanuric acid, which is used to reduce chlorine loss as a result of ultraviolet light exposure, is not recommended for indoor pools or hot tubs and is prohibited in two states ; adding this chemical reduces the antimicrobial capacity of free chlorine. "

I'm not exactly sure what they mean by this ( & how this affects us)
" cya reduces antimicrobial capacity of free chlorine "
perhaps some of the chemistry majors here can explain farther the effects of this statement.


I also thought that these guidelines were pretty standard ( & worthwhile):

To reduce the risk for Pseudomonas dermatitis and the transmission of other waterborne pathogens, pool and hot tub operators should
1) adhere to pool and hot tub recommendations and regulatory requirements for pH and disinfectant levels;
2) have a thorough knowledge of basic aquatic facility operation;
3) provide training for pool staff on system capabilities, maintenance, and emergency alert procedures of remote monitoring systems;
4) closely monitor pool and hot tub free chlorine measurements during periods of heavy bather loading;
5) monitor hot tub disinfectant levels closely because the higher temperatures maintained serve to dissipate chlorine rapidly;
and 6) understand appropriate use and effects of cyanurates on disinfection and testing.
In addition, remote-monitoring companies should be timely in notifying swimming-facility staff about low disinfectant levels.
Swimmers should be educated about the potential for waterborne disease transmission in pools and hot tubs, which could increase advocacy for improved maintenance and monitoring by pool operators.

[chem geek]

Personally, and especially in a hot tub, I would use the smallest amount of CYA you can get away with that will give you sufficient chlorine buffer and protection from sunlight (UV) so that you won't run out before adding more while not being so much that it cuts down chlorine's effectiveness too much. That probably means 30 or less, which makes it hard to measure (unfortunately). The main difference between the hot tub and the pool is that the bug that causes "hot tub itch" thrives in the hotter temperatures and is a much harder to kill bug than E.coli which is a moderate-to-kill bug (most others are easy-to-kill). The standard set for pool disinfection (650 mV) kills easy bugs in less than a second and E.coli in seconds to a few minutes (depending on whose data I look at), but the Pseudomonas are a hard-to-kill bug.

I don't want this thrown into The China Shop so instead I refer you to this post where I presented my results a while back. The bottom line is that CYA significantly reduces chlorine's effectiveness because it binds up the chlorine into a form (technically one of several combinations of CYA plus chlorine called chlorinated isocyanurates) that while significantly protected from breakdown from sunlight (UV), has minimal disinfecting and oxidizing ability. Think of it like this: CYA converts chlorine into a form that is better protected from sunlight, but is not "active" for disinfection. It is like being in reserve and can be converted to the active form as the active form gets used up, but it is not itself an active form. Chlorine "effectiveness" depends on how much chlorine is in the active form and doesn't matter on how much is in "reserve".

At a pH of 7.5, CYA reduces chlorine's effectiveness by a factor that is 75% of the ppm of CYA. So, 30 ppm CYA reduces chlorine's effectiveness by a factor of 0.75 * 30 = 22.5 so that chlorine in 30 ppm CYA is only 1/22nd as powerful as with no CYA. This is because there is only 1/22nd the amount of the disinfecting and oxidizing form of chlorine (HOCl) present since most of it is bound up with CYA and not effective. This rule of thumb only applies when the amount of CYA is much higher (about 3 times or more) than the chlorine level. Here is a set of graphs that shows how little disinfecting chlorine there is with 30 ppm CYA. Let me know how this can be presented in a way that doesn't scare people off. It's important information to know, but needs to be made less technical.

Richard

[RavenNS]

Okay, let's see if I "get" this...
suppose I have cya 30 & I'd like my disinfectant to be at 6ppm...
I then add enough to make it 7.5ppm ...
(based on it being aprox. 25% less effective... yes?)

[waterbear]

what it does say about Cya is:
" cyanuric acid, which is used to reduce chlorine loss as a result of ultraviolet light exposure, is not recommended for indoor pools or hot tubs and is prohibited in two states ; adding this chemical reduces the antimicrobial capacity of free chlorine. "

Precisely, CYA is NOT recommeded for use in indoor pools and hot tubs. Indoor pools and hot tubs are problematic for a number of reasons. And if my understanding is correct of the states that ban CYA in commercial pools that they do allow variences on that and that pools that do not use CYA must use ORP controllers and feed systems to maintain the chlorine levels. I was only aware of upstate NY requiring this. I would be intersted in what other state has passed this restriction. The main thurst of this article just indicated the need for GOOD water testing and maintenace on a regular basis and an understanding of what is involved....just like we all promote, practice, and teach here in this forum!

[RavenNS]

side note:
I would be interested in finding out if Canada has also recommended not using CYA in indoor or public pools.
also, the states that have banned this chemical; was there any basis for this other than reducing chlorine effectiveness ? ( other problematic health factors associated with this chemical ?)

[chem geek]

Okay, let's see if I "get" this...
suppose I have cya 30 & I'd like my disinfectant to be at 6ppm...
I then add enough to make it 7.5ppm ...
(based on it being aprox. 25% less effective... yes?)

No, it's much worse that this. A CYA of 30 makes the FC chlorine amount 0.75*30=22.5 TIMES less effective. If you want your disinfectant (HOCl) to be at 6 ppm (which is WAY too high), you would need 22.5 * 6 = 135 ppm FC! The reality is that you need very, very little actual disinfecting chlorine to kill bugs and to oxidize simple organics (ammonia, urea, etc.). The "min/max" ranges in Ben's chart roughly correspond to disinfecting chlorine (HOCl) levels of 0.03 to 0.07 ppm. And yes, this means that the equivalent without CYA would mean maintaining FC levels of around 0.03 to 0.07 ppm, but obviously this is nearly impossible to do since it is so small and gets used up easily so instead you put in extra FC "in reserve", typically at least 1 ppm or 2 ppm. The "min/max" numbers in Ben's chart are at various CYA levels and are roughly the amount of FC needed to get to the 0.03 to 0.07 ppm disinfecting chlorine (HOCl) level. He figured all of this out through experience so his table doesn't exactly correspond, but it's pretty close (though the "shock" column doesn't correspond very well).

The German standard for chlorination is for 0.2 ppm chlorine, which I believe is without CYA (it had better be without!). Historically, before CYA was in widespread use, very low chlorine levels of 0.2 or 0.5 ppm and certainly not more than 1 ppm were the "standard" so long as such levels could be consistently maintained. Presumably these were indoor pools or somehow had their chlorine replenished at rapid rates since in sunlight about half of the chlorine can get consumed every half-hour.

Richard

[waterbear]

No, it's much worse that this. A CYA of 30 makes the FC chlorine amount 0.75*30=22.5 TIMES less effective. If you want your disinfectant (HOCl) to be at 6 ppm (which is WAY too high), you would need 22.5 * 6 = 135 ppm FC! The reality is that you need very, very little actual disinfecting chlorine to kill bugs and to oxidize simple organics (ammonia, urea, etc.). The "min/max" ranges in Ben's chart roughly correspond to disinfecting chlorine (HOCl) levels of 0.03 to 0.07 ppm. And yes, this means that the equivalent without CYA would mean maintaining FC levels of around 0.03 to 0.07 ppm, but obviously this is nearly impossible to do since it is so small and gets used up easily so instead you put in extra FC "in reserve", typically at least 1 ppm or 2 ppm. The "min/max" numbers in Ben's chart are at various CYA levels and are roughly the amount of FC needed to get to the 0.03 to 0.07 ppm disinfecting chlorine (HOCl) level. He figured all of this out through experience so his table doesn't exactly correspond, but it's pretty close (though the "shock" column doesn't correspond very well).

The German standard for chlorination is for 0.2 ppm chlorine, which I believe is without CYA (it had better be without!). Historically, before CYA was in widespread use, very low chlorine levels of 0.2 or 0.5 ppm and certainly not more than 1 ppm were the "standard" so long as such levels could be consistently maintained. Presumably these were indoor pools or somehow had their chlorine replenished at rapid rates since in sunlight about half of the chlorine can get consumed every half-hour.

Richard

Actually, the recommended FC level for hot tubs is usually in the range of 3-6 ppm.