Not having success with BBB in my hot tub

[keithw]

I tred BBB in my hot tub but I'm just not having any luck. I cannot maintain a decent CL level for more than a day. It's 120 gal stand alone hot tub. The prob is that my kids and I get the "hot tub rash" easily and sure enough, got it a week ago after only 1 month with BBB. I hate to say it, but I did Baquacil for three years and never had a problem. The is just no room for error with BBB with hot water and in a tub that size I guess. You miss one day and you're screwed. I could go a week neglecting chemicals with Baquacil and not have any problems. Unfortuantely, with Baquacil the water is almost constantly clouded.

[duraleigh]

Yeah, I'm not a hot tub person but I'm pretty sure I've read Chlorine is not a really good sanitizer for them......I think because of the higher temps.

Again, I'm just guessing but I think I remember Bromine being the most commonly used disinfectant.

[chem geek]

I'm sorry you aren't having success with BBB in your hot tub. Is your hot tub outside and exposed to sunlight? If so, for how long and do you cover your hot tub when not in use? Can you post a set of typical numbers of spa chemistry parameters (pH, TA, CYA, FC, CC if any, I doubt you have or need much CH)?

Perhaps we can figure out why you were losing so much chlorine. Also, with regard to hot tub itch, this is caused by a particularly difficult-to-kill bacteria (Pseudomonas aeruginosa) so particularly high disinfecting chlorine levels are required and that means not only keeping FC up, but not having CYA too high (if an outdoor spa frequently exposed to sunlight). On the other hand, not using any CYA will lead to a rapid loss of chlorine in sunlight and will also increase its rate of loss through outgassing.

It is true that the chlorine will have a tendency to outgas from the spa more readily due to the higher temperature and the aeration. It turns out that the outgassing is theoretically also very much a function of the amount of chloride ion (salt) that is in the water. If you had a TA of 100 and CH of 30 resulting in a salt level of around 50 (ppm NaCl), then with no CYA this would theoretically outgas chlorine at a rate of around one-twelfth of your FC per day. However, if you had 200 ppm of salt in the water (built up from the chemicals you add over time, including chlorine) then you would outgas chlorine at one-third of your FC per day. If your CH was high, then your salt could be high because CH is increased via Calcium Chloride (and the chloride increases the rate of chlorine outgassing).

It may be that a solution to your situation would be to use a small amount of CYA (10 ppm or less if you can approximately measure that -- most measurement kits only go down to 30 and some down to 20) to cut down the chlorine outgas rate, but not too much since you want high disinfecting chlorine levels. Regularly refreshing the water so that it keeps the salt level down would also help. If you use CYA, then you can safely use quite high levels of chlorine up to 10 ppm and the combination of high FC and a little CYA should give you a decent reserve so you don't "run out" of chlorine. I admit that keeping the "low, but not too low nor too high" CYA level is tricky.

Perhaps others who use BBB to maintain their hot tubs (hopefully successfully) can give you their tips as well. I don't have a hot tub so am speaking from theoretical science, not experience. And I agree with Dave that most people with hot tubs use a Bromine or Bromine/Chlorine combination precisely to combat this "rapid loss of chlorine" problem as well as to reduce the "chlorine smell" (probably from outgassing).

Richard

[keithw]

Richard,

I'll test it fully tonight and post the results. I have been dumping powdered stabilized shock into the hot tub regularly because it seemed to get the CL up quicker and because I was trying to get at least a little CYA into the tub. Bleach doesn't seem to get the levels up as high as bleachcalc would suggest that it should. I also salted the water up to 2000PPM (I think!) I will check that as well.

My tub is outdoors, but covered 24/7 except when we are in it.

My disdain is that there appears to be sooo little margin for error. It seems to go from 5+PPM CL to nothing in a day! I used to get the rash regularly with Bromine as well. I am just suprised that Baquacil seemed to be so much more effective at killing off Pseudomonas aeruginosa.

[chem geek]

First you started with no CYA and using bleach...
With no CYA (and with 2000 ppm salt), you would outgas virtually all of your FC in about 10 hours! Even worse, without CYA you can lose half of your FC in just 30 minutes due to sunlight! So even though you covered your tub when not in use, even short-term use during the day would really eat up the FC very, very quickly if there was no CYA.

Then you used powdered stabilized shock...
Powdered stabilized shock was probably Di-Chlor (since that doesn't change pH much and it dissolves quickly). The small size of your hot tub means that adding only 1/4 ounce of Di-Chlor would increase your Free Chlorine (FC) by 8.6 ppm while also increasing your Cyanuric Acid (CYA) by 7.9 ppm. So basically when using Di-Chlor, you add about as much CYA as you do FC, but the FC goes away while the CYA does not!

So it's no wonder that the chlorine wasn't effective after a few doses of Di-Chlor. Your CYA levels probably are through the roof -- if you can test that and let us know, that would be very interesting. As for BleachCalc, my guess is that your hot tub is larger than 120 gallons -- are you sure of that number as this is small and would be for a 2-person hot tub (5-6 person tub is around 375-400 gallons)?

A high CYA level would explain why adding chlorine wasn't effective at killing hot tub itch. That still leaves the issue of the chlorine getting used up so quickly even after you started using Di-Chlor. The high salt level would certainly contribute to chlorine getting outgassed, but the high CYA would cut that down significantly and would also protect the chlorine from sunlight. So that leaves the other source of chlorine consumption, namely killing bugs and oxidizing organics. I'll bet that your CC levels are high and that the chlorine is struggling to keep up with everything (such as sweat) introduced into the relatively small volume of water.

When you were using Baquacil...
I don't think it's so much that Baquacil was better at killing Pseudomonas aeruginosa than chlorine, but that when the chlorine was used up (and not there) or when it was in the presence of a lot of CYA, then it was not effective. So the key is to get the chlorine level up and to stay up and to not have too much CYA present. Also, when you were using Baquacil, did you add both the biquinide (PHMB) and hydrogen peroxide? The former kills bacteria and algae, but only the latter oxidizes organics and most of the junk in spa water is organics (sweat).

My guess at this point is the following. When you used Baquacil, you were adding biguinide (PHMB) but not hydrogen peroxide. So while you were killing bacteria (including hot tub itch) and preventing algae, you weren't oxidizing organics (e.g. sweat) so when these built up that caused the water to get cloudy. When you switched to using chlorine, most of it is getting used up oxidizing the organics and perhaps you never got to a point where you oxidized all of them so just saw perpetual chlorine demand (and with no CYA initially and high salt levels you were also using up chlorine through outgassing as well as breakdown from sunlight). After you added Di-Chlor, the CYA made the chlorine ineffective and you got hot tub itch.

Richard

[Tomcat]

Why sweat it with BBB and a tub to save, literally, pennies. Buy some bromine and a floater and be done with it. $20 for bromine lasts me six months. Borax if you need to bump up the ph and dry acid ($3 or $4 for a bottle that's lasted well over six months) to bring it down. Hut tub maintenance is very, very cheap, compared to a pool, and I really don't see where any big savings can be had. MHO

[keithw]

Hmm, lots of questions to answer...

First Tomcat:
I'm not at all concerned about saving money (or I wouldn't consider going back to baquacil!!) I was just trying to get a clearer (and cleaner feel) to my hot tub than what I was getting with baquacil and really love the effect of BBB in my pool. I used to use bromine as well many moons ago with my older hot tub and also experienced the hot tub itch crud on occassion so thought that I'd try chlorine instead. Honestly it has been so miraculous on the pool I figured that with a tad of maintenance it would be as good in the tub.

Richard:
Yes it's 120 gal according to the manufacturer. It's a three seat, really two seat and a lounge. Pretty small, but that's all I wanted and needed.

Interesting thought on the di chlor and CYA being too high. I will definitely test tonight. I was only adding a few teaspoonfuls at a pop and thought that the CYA would not go very high at all from such a small amount but perhaps it's through the roof. Never checked because I assumed it'd be real low.

In regards to what I was adding with the Baquacil, I'd have to say....I don't know! I just bought the stuff they said to in the book and stuck it in when the test strips recommended it. They were called: A. Sanitizer. B. Shock (recently they changed the name to oxidizer.) C. Waterline control. Also obviously PH & alk up and down, and their "water clarifier" that didn't work worth a darn....

Now for a question on Pseudomonas aeruginosa...Knowing that one has it in one's tub, how high would the CL need to be and for how long would it need to be there to kill it off?

In regards to losing CL to sunlight. I only go in at night so UV shouldn't be an issue.

[chem geek]

In regards to what I was adding with the Baquacil, I'd have to say....I don't know! I just bought the stuff they said to in the book and stuck it in when the test strips recommended it. They were called: A. Sanitizer. B. Shock (recently they changed the name to oxidizer.) C. Waterline control. Also obviously PH & alk up and down, and their "water clarifier" that didn't work worth a darn....

Now for a question on Pseudomonas aeruginosa...Knowing that one has it in one's tub, how high would the CL need to be and for how long would it need to be there to kill it off?

The "A. Sanitizer" was probably Biguinide (PHMB) while the "B. Shock or Oxidizer" was probably Hydrogen Peroxide. So the shock should have oxidized organics and you should not have had cloudy water, but then again who knows what happened...

As for Pseudomonas aeruginosa, it looks like the CT (chlorine concentration times time in minutes) values for this bug are on the order of 50-70 which would mean it would take about 20 minutes to kill 99.99% of the bugs at a 3.0 disinfecting chlorine level, but I do know that the commercial spas study measured pseudomonas and found that the 650 mV ORP level which roughly corresponds to the 0.011 ppm disinfecting chlorine level was sufficient to prevent these organisms from growing. However, once they are started, they can form biofilms and require much more chlorine to kill which is what the 50-70 CT value represents. Bottom line is that Ben's best guess chart is probably sufficient for preventing it (his minimums are around 0.02-0.03 disinfecting chlorine), but you need to shock regularly to get rid of it once it's there. Since it is so hard to control sanitation levels in the small volume of water, setting an initial target of around 5 ppm chlorine would be good and try never to drop below 3 ppm. You mostly need that amount of chlorine simply to oxidize the organics, that is, to never run out. If you use any CYA at all it should be a very small amount (< 10 ppm) so that you can easily shock to get to high chlorine levels when needed.

And I agree with previous posters that bromine can be easier to use in this sort of situation, but I also understand your desire to get that wonderful BBB feel. My hunch is that if you shock your spa and keep it at shock levels until the chlorine doesn't drop anymore, then you'll have a clean-water starting point. Then any chlorine usage would be related to your usage of the water and you'll just have to drop in an amount of chlorine after each use. Some websites even recommend a shock level after each use, but that's probably for heavier usage (i.e. 6 people in a 4-5 seater).

Richard

[keithw]

Richard,

Well just got home and checked my levels and you are correct on the CYA. Tested with Taylor K-2006 so should be pretty accurate.

FC 10.6
CC 1.2
CYA 100
ALK 130
PH 7.5

Since the CYA is so out of whack, I guess I will just drain and start over and give it one last shot.

My hunch is that if you shock your spa and keep it at shock levels until the chlorine doesn't drop anymore, then you'll have a clean-water starting point.

My problem has been that I could never reach a point where the CL wouldn't drop any more. Gonna give it one more shot though.

[chem geek]

Gonna give it one more shot though.

When you do the drain and refill, there will still be residual CYA in the pipes and stuck to the walls that you can't get rid of so just be aware that there will still be a small amount (probably < 5 ppm, perhaps only 1 ppm though you can try testing for it to see). I suggest you not add salt to see if that makes any difference. Notice that you have a large FC now, but also have CC which makes me think that indeed there is something consuming a lot of chlorine in your tub.

I'm keeping my fingers crossed that the chlorine will hold this time, at least after some initial use. Keep us posted.

Richard