Hot tub with BBB & Borax

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FlyboyTR

FlyboyTR

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Jul 5, 2009
82
Mobile, AL
In preparing for the new pool...we are trying the BBB with our hot tub. The following are our numbers over the past several days. After testing the "fresh" water I did the following: 26oz Borax, 13oz MA, 1oz Dichlor. The numbers below start after the initial chemicals were added. Is this going in the right direction?

Date.......Time. . .FC...PH...TA...CH...CYA
07/08/09 7:00 PM, 2.0, 8.0, 150, 150
07/09/09 5:31 PM, 1.2. 8.3, 150..................1oz Dichlor, 6oz MA
07/09/09 6:10 PM, 22,. 7.2, 90
07/10/09 8:26 PM, 8.5, 8.0, 90 ..................3oz MA, 1oz Dichlor after use
07/12/09 7:40 AM, 5.0, 7.7, 70

After reading multiple posts, I am a little confused about where the FC should be. Also I am still a little lost with the MPS...how and when. Thanks!

FlyboyTR
 
Jason,
I read the one started by Nitro...is this all one and the same...or did I miss it? If this is the one, I have read it several times. It all seems simple at first but then I get a little confused along the way. It's possible I'm reading it too late at night! :-D I will go back and see if I can unlock the secret of the FC.

FlyboyTR
 
Looks like you're having some trouble with the pH despite adding borax. In my tub there's a separate control for adding air to the jets; if I leave the air off when I'm not using it, the pH is very stable. Do you have the air on all the time?

The best way to get used to your tub's "chlorine demand" is to be consistent about when you test. You mostly reported testing in the evening, which is fine, but then once was in the morning, which will throw you off a little.

I don't use the MPS much, maybe after a soak to keep the chlorine from being used up too fast. As often as not I don't remember, and it just means a little more chlorine the next day. MPS just supplements the chlorine.

What kind of chlorine test are you using? You're reporting it as FC but if it's the yellow drops then it's really TC (= FC + CC) and MPS shows up as CC for a while after you use it.
--paulr
 
PaulR,
I am using the TF-100 test kit for the FC. I have a hard time reading the little color kit that reads TC. My air jets stay off unless we are using the spa...which is usually nightly. I will return to reading the post on chlorine again...hopefully more will stick this time around.

I have always checked chemicals in the evening...just had to be nosey and checked it that morning. ...new test kit! :oops:

Thanks again for your help.

FlyboyTR
 
FlyboyTR said:
These are my numbers for this evening.
PH - 7.5
TA - 70
FC - 4.5
CC - 1.5
TC - 6

Am I correct in that the FC + CC + TC?
Click to expand...

I am just a beginner too, but I do know that you are correct in that FC + CC = TC. Now I am thinking all of your results look good except for your CC. I know if my pool shows a CC reading of > 0.5, that means its time to shock the pool. But with your spa is the higher CC reading OK because some of it is really MPS? How would one know then when its time to shock? My new spa arrives in 2 days so I am trying my best to learn too!
 
If MPS (non-chlorine shock) is used, then yes, this will generally show up as CC (it can even show up as FC if the concentration is high enough or is measured very soon after addition). MPS use is not necessary; it's an option. Even if MPS is not being used, having CC soon after a soak is not uncommon and nothing to worry about (it takes about an hour or so to break down the urea and ammonia from your sweat/urine and in spas the bather load is high).

If you measure significant (> 0.5 ppm) CC just before your next soak, then you should consider shocking with chlorine, especially if you have a higher than normal chlorine demand. Usually with a tub not being used, you would lose around 25% or so of the FC in a 24-hour period. If you lose more than 50%, then you've got something in the tub that needs to get oxidized so should shock it by raising the FC level.
 
chem geek said:
If MPS (non-chlorine shock) is used, then yes, this will generally show up as CC (it can even show up as FC if the concentration is high enough or is measured very soon after addition). MPS use is not necessary; it's an option. Even if MPS is not being used, having CC soon after a soak is not uncommon and nothing to worry about (it takes about an hour or so to break down the urea and ammonia from your sweat/urine and in spas the bather load is high).

If you measure significant (> 0.5 ppm) CC just before your next soak, then you should consider shocking with chlorine, especially if you have a higher than normal chlorine demand. Usually with a tub not being used, you would lose around 25% or so of the FC in a 24-hour period. If you lose more than 50%, then you've got something in the tub that needs to get oxidized so should shock it by raising the FC level.
Click to expand...

Let me see if I got it. When using MPS, its very important to check your FC and CC levels at about the same time each day and preferably just before a soak, not after. Then evaluate the need for shock treatment based on the CC level AND the decrease in FC from the previous day. If CC is > 0.5 and the 24 hour FC drop is > 50%, then its time to shock. If CC is > 0.5, but the FC hasn't dropped > 50% since the previous day, there is no need for a shock and the CC level may just be reflecting the MPS in the spa? I hope I have this right because it is actually seeming to make sense to me. :goodjob:
 

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The reason to be consistent about when you test is so you learn how the tub behaves, and learn its typical chlorine demand. The consistency is not because of MPS, you would want to be consistent even if you never use MPS. Once you know how the tub behaves, you'll be better able to tell when something unusual is going on.
--paulr
 
Ok, I am on a roll now. If using MPS, you probably need to check your FC for a second time in the evening if you made any cholorine additions based on the first set of numbers from that evening. In order to look for a 50% drop in 24 hours, you first need to know where your peak started at.

You know, I'm a pharmacist in the real world and this is really starting to remind me of some of the principles of drug dosing and elimination in a living system. I suppose when you come right down to it, a spa is a living system. Its just a living system that we want to keep mostly dead. Kinda of the oposite of the goal in pharmacy school. :lol:
 
My numbers yesterday evening were:
PH - 7.5
TA - 70
FC - 4.5
CC - 1.5
TC - 6

This evening they are
PH - 7.5
TA - 70
FC - 4
CC - 0.5
TC - 4.5

My CC is dropping and I've only lost 0.5 off the FC in the past 22 hours. If I understand this right... since my CC has dropped to 0.5 ( the minimal acceptable level) and the FC has also dropped (but is still >3) can I assume that all is well with the sanitation? We plan to use the tub this evening. We will use all the air jets so I can check the PH rise. I will recheck everything afterwards to see what FC drop has taken place and then raise the FC to 6. I hope I'm finally going in the right direction!
 
FlyboyTR said:
My numbers yesterday evening were:
PH - 7.5
TA - 70
FC - 4.5
CC - 1.5
TC - 6

This evening they are
PH - 7.5
TA - 70
FC - 4
CC - 0.5
TC - 4.5

My CC is dropping and I've only lost 0.5 off the FC in the past 22 hours. If I understand this right... since my CC has dropped to 0.5 ( the minimal acceptable level) and the FC has also dropped (but is still >3) can I assume that all is well with the sanitation? We plan to use the tub this evening. We will use all the air jets so I can check the PH rise. I will recheck everything afterwards to see what FC drop has taken place and then raise the FC to 6. I hope I'm finally going in the right direction!
Click to expand...
These are the numbers again tonight after a 20 minute soak with everything turned on.
PH 7.6
FC 1
CC .5
TC 1.5
I am still going to raise my FC to 6. Based upon The Pool Calculator, I need to add .5 oz of Dichlor. Should I have done more?

My next issue... the CYA. If I understand right from reading... I need the CYA to be around 20-30 (or possibly up to 50?). The text said that for every 10ppm of Dichlor, I get 9ppm CYA. According to the Calculator in am gaining 5ppm of FC for every .5oz of DIchlor. As of tonight I have added 5.5oz of Dichlor for a total increase of 55ppm and 49.5ppm of CYA. If this is accurate...I have overshot on my CYA. If so...I should have started using Chlorox a couple of days ago! Am I still on track...or do I have this screwed up as well! Thanks again for everyone's help...sincerely appreciated!
 
In a hot tub that spends most of its time covered up, the purpose of CYA is not to protect the chlorine from sunlight but to act as a chlorine buffer. That's why 20-30ppm CYA is enough. It's not that 50 is bad, it's just more than you need for that situation. You'll need to keep the FC a little higher than otherwise, but it's no reason to dump and refill the tub.

I would actually test the water, rather than rely on the calculation. There's some degree of fuzz to all this and testing will give you a better handle on what has happened. As you gain experience with the dichlor/bleach technique you'll get a feel for how much dichlor you need after each refill.
--paulr
 
Paul,
Thanks for the quick reply! I shall assume that my "fuzzy" math on the CYA is close. I was going to use Chlorox tonight...but when I pulled it out of the laundry closet it was some kind of Linen Fresh Chlorox...and did not state what % it was...so I went ahead with the Dichlor. I'll start tomorrow with the Chlorox.

I am usually quick with figuring things out...but this spa and pool chemestry is just beating me up! :hammer: Hopefully...I am getting there! Thanks again to everyone for the help and patience! :-D
 
As for how much chlorine you need to use after each soak, you want to use enough so that you still measure a residual FC (at least 1 ppm, usually a bit more) before the next soak. The rough rule of thumb is that every person-hour of soaking in a hot (100-104F) tub requires 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of MPS non-chlorine shock. So if it's just one of you soaking for 20 minutes, that's a little over 1 teaspoon of Dichlor or 1-2/3 fluid ounces of bleach. If two of you soak for 20 minutes, then it's double these amounts. However, your own testing is your best guide.

[EDIT] Note that I incorrectly wrote 1-2/3 teaspoons instead of fluid ounces for the amount of bleach in 20 minutes. [END-EDIT]
 
I am beginning to see the reason for daily checking after startup...so that you learn what your system needs and how it reacts to different loads/use. The simple break down on the bather load/hour certainly helps. Chem Geek, you and many others provide and infinite amount of knowledge and help to a lot of people that are swimming in the dark! Thanks again!
 

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