Water chem ?s, with regards to h2o in spa

[bbrock]

Hi TFP'ers,
This is applicable here b/c mostly it pertains to water chem, not just spas. As such, that is why posting here.

I have bromine spa. Changed out water on Sat. following this site, as I usually do:
How do I use Bromine in my spa (or pool)?

and I also use this site for reference too:
How do I use Chlorine in my Spa (or pool)?

?s
1. I float bromine tabs. As such pH typically drops. This water change, decided to try to keep higher TA to see if that will slow the drop. Old water TA was ~80. This water I decided to start water at TA 120 to just see if that will help. Overshot when added 2 oz 2 tsp baking soda and water at TA 130, which is fine. pH was 7.2 so added 1 oz borax. Then I added 2 oz chlorine to shock/activate bromide bank. When rechecked, pH 8, Br 8, and TA 130. Should I start chasing the pH? Please refresh my memory as I thought the pH rise from my 7.6 just d/t having added and shocked with the chlorine, right?

2. I already planned to start with the TA at 120 or 130 and see what happens over the next few days/weeks if the pH will still drops as it did on old water. Objective is simply to see if keeping higher TA will slow the naturally tendency for it to drop from the bromine tabs. Sound plan?

Tx in advance.
B

 

[kimkats]

Re: Water chem ?s, but with regards to h2o in spa

No ideas from me but here is a bump

 

[bbrock]

Re: Water chem ?s, but with regards to h2o in spa

Tx Kim. Always appreciate your help. Perhaps I should move my post to the Spas forum. What do you think? I placed here b/c I thought it would be more applicable. Not sure if the move would stir up some input.

 

[kimkats]

Re: Water chem ?s, but with regards to h2o in spa

I will move it for you. Lets see how that works!

 

[jza1736]

I've found The high TA in my bromine spa to be a pain.

My spa spec asks for TA 80-120. When I tried that I was chasing high PH. Lowered that and the TA would go low. I did that for 2 weeks.

My spa likes TA of 50. My PH stays around 7.6-7.8.

I doubt keeping the TA high will help you. It might cause more headaches.

 

[jmasone]

I've found The high TA in my bromine spa to be a pain.

My spa spec asks for TA 80-120. When I tried that I was chasing high PH. Lowered that and the TA would go low. I did that for 2 weeks.

My spa likes TA of 50. My PH stays around 7.6-7.8.

I doubt keeping the TA high will help you. It might cause more headaches.

I thought it was just me. When I maintained a TA around 80, my pH would always read high. When the pH naturally dropped to 60, pH was fine. Now, TA is stabilized at 60 and pH is stabilized at 7.4-7.6

 

[dlleno]

Same here

One point to make up front is that from an equipment and vessel standpoint , the saturation index can be negative in an acrylic spa because there are no gunite walls to give back calcium. I find that chasing a recommended number for TA is not fruitful because the recommended number is usually grounded in the saturation index and is a recipe for ph drift. I find much happiness at low TA numbers for this reason. Chase pH, and let TA fall where it may. I've been as low as 40 .

The caution that must be added here is that when TA gets too low (below 40 ) you risk a precipitous drop in pH. So the reason to measure TA is to monitor that, not to achieve a specific number.

As an aside, bromine with an ozone generator is great because the ozone assists in the oxidation of bromide salts

 

[bbrock]

Tx for the replies as I was not being notified of responses automatically. Any reason why notifications were sent to me of responses moderators?

I actually have found findings counter to what you have stated dlleno, jmasone, jza1736. Since I have changed the water and posted above, I lowered my TA from 130 to 120 b/c my pH climbed to and stayed around 8.2+. And, realize this is despite the net acidity from my bromine tabs. I even invert my bromine floater to displace all the air, which ensures and maintains a higher bromine level in my spa. So, even after a few days of higher bromine levels I thought I'd see a drop in the pH, but I didn't. Thus, I figured I could chase the pH, but what was the true contributing factor, it had to be my TA (see below). On my old water, with a TA of 70 or 80, I'd regularly see the pH drop due to the net acidity of the bromine tabs. But this was not happening since my water change.

I put in 2 oz of MA (I think 1 oz at a time) to lower the TA from 130, and then aerate to increase my pH. After the second oz of MA and aeration, I got my TA to 120 and pH stayed at 7.8. This was good enough for me. I have even been inverting my bromine floater periodically to displace the water and ensure good bromine levels, and my pH has been holding steady at 7.8.

So, in summary, I have found that maintaining a slightly higher TA has assisted me so far. The basis for my theory that the TA was more important to get right vs. chasing the pH was taken from that link I supplied in my 1st post: How...chlorine in pool or spa? Main point I considered from said link:
Let me repeat the last sentence, because it's the single most important thing to keeping your water balanced. The key to having balanced water, without pH drift, is having the correct TA level. If you find your pH rises too high (>8.0) after using your tub, your TA is too high, and needs to be lowered. If you find your pH is too low and/or your water is continually acidic, your TA is too low and needs to be raised. By fine tuning your TA, you can get your pH perfectly balanced, that rarely needs adjustment.

SO, what's a good TA then? Because spas tend to have a lot of aeration from jets and because the water is hot, it is best to keep the TA low at around 50 ppm.

OK, how do we adjust TA then? If TA is too low, you just add Baking Soda to raise it. However, if TA is high, it's little more involved. You'll need Acid (Dry or Muriatic). Depending on how high your TA is will depend on how long it will take you. Plan on it taking around an hour to decrease TA by 100 ppm. So if your TA is 300 ppm, plan it taking around 2-3 hours. First, uncover your tub and turn on all your jets, air, blowers, waterfalls etc. Test your pH. When it's greater than 7.8, add enough acid to bring it down to 7.0. Keep aerating until your pH is 7.8 again (about 30 min), then add more acid and repeat. Every time you add acid you're lowering your pH and TA. When you get your TA tuned perfectly, your pH will rise to a level (i.e. ~7.6) and stop, then you know you're at your ideal TA level. If your pH is rising too high (>8.0), bring your TA down a little more. If your pH doesn't rise enough from aeration (after an hour or more), you over shot it and need to add a little Baking Soda to raise your TA. After a few days/weeks of monitoring it, you'll get your TA tuned perfectly. You may need to add a little Dry Acid once a week or two, but your water should be well balanced at that point.

 

[kimkats]

Tx for the replies as I was not being notified of responses automatically. Any reason why notifications were sent to me of responses moderators?

I took a peek and you do have your settings set to receiving instant notification so I am not sure why you did not get them. Did you check your junk email box? Let me know what you find.

Kim

 

[jseyfert3]

I think most people here run Chlorine spas. Liquid chlorine has very little affect on pH, so a lower TA of around 50 is needed. If you use a bromine floater which is acidic, a higher TA will be needed to maintain a steady pH.

So what you see makes perfect sense.