T.A. in salt water???

reynolds357

Well-known member
Jun 14, 2013
60
Atlanta, GA
I have been pondering for several years why maintain Total Alkalinity in salt water pool. This year, I totally abandoned maintaining T.A. and observed no negative isdues I could observe. I used half the acid I used in previous seasons. Used no baking soda, and had no problems even at end of season when alkalinity was under 20. What am I missing or not thinking out??
 

AUSpool

Bronze Supporter
LifeTime Supporter
TFP Guide
Sep 23, 2015
750
Brisbane, Australia.
The immediate thing that comes to mind is your CSI. Damage to your pool surface. And then there’s pH and how your TA affects you pH and in turn your FC level. All a bit hard to get exact without any recent test results or pool info.
 

Newdude

Well-known member
Jun 16, 2019
4,485
NY
You are finding out what most of us that ‘gave up’ found out. That if you let it settle to it’s happy place, it will stay there and not need babysitting. I can go a month or more without touching the PH. After the initial TA adjustment I do not touch it for the rest of the season. If I fiddled with either all the time it would be every other day. The pool store wants you constantly adjusting both PH and TA to make them swing. Like any swing, it stays in motion and you’ll need to buy more chemicals to swing it back the other way.

I found this out by accident after always chasing the PH. One day I had enough and just let it ride. I went the rest of the season with no ill effects. I learned why a few years later here.

For both your SWG and plaster you need to have your CSI in range as well, but as long as everything is ‘in range’ then you are fine.
 

reynolds357

Well-known member
Jun 14, 2013
60
Atlanta, GA
The immediate thing that comes to mind is your CSI. Damage to your pool surface. And then there’s pH and how your TA affects you pH and in turn your FC level. All a bit hard to get exact without any recent test results or pool info.
Couple days ago, at 5:30 pm.
FC 2
Tc 2
Ch 160
Ta 20
Cya 30
Swcg is running at 12%
In mid august swcg has to be turned up to 25%.
Pool is 32000 gal.
SWCG at 100% would make equivalent of 1.5 lb 68% cal hypo per 24 hr. (According to salesman anyway)
 
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reynolds357

Well-known member
Jun 14, 2013
60
Atlanta, GA
You are finding out what most of us that ‘gave up’ found out. That if you let it settle to it’s happy place, it will stay there and not need babysitting. I can go a month or more without touching the PH. After the initial TA adjustment I do not touch it for the rest of the season. If I fiddled with either all the time it would be every other day. The pool store wants you constantly adjusting both PH and TA to make them swing. Like any swing, it stays in motion and you’ll need to buy more chemicals to swing it back the other way.

I found this out by accident after always chasing the PH. One day I had enough and just let it ride. I went the rest of the season with no ill effects. I learned why a few years later here.

For both your SWG and plaster you need to have your CSI in range as well, but as long as everything is ‘in range’ then you are fine.
Thats the point I had gotten to with my old pool. With the salt water, I never have to raise ph. Its always pour in muriatic to lower it. It got me thinking why keep the TA high if my PH never goes down?
 

mgtfp

Bronze Supporter
Mar 5, 2020
425
Melbourne, Australia
Your carbonate alkalinity is basically in equilibrium with atmospheric CO2 at pH 7.5, i.e. your pH shouldn't rise above 7.5 due to outgassing. Further continued pH rise would indicate other mechanisms like undissolved Cl2 gas produced by the SWG out-gassing. I'd be interested in your observations there.

You need to keep in mind that you have not much of a buffer system in your water. Adding 30ppm worth of CYA will for example drop your pH down to below 6.8 (from 7.5).

Not having a buffer also means that the fluctuations within your chlorination cycle will be quite significant. Creating 4ppm with your SWG will temporarily raise your pH to 8.3 until these 4ppm have been consumed again.

Adding enough bleach to get you to SLAM FC will push your pH to 8.6 (even after initially lowering it to 7.2). That might be a metal staining risk. If you corrected that during during the SLAM to 7.8 by adding MA, you'd run the risk of dropping down to pH 6.8 once FC levels are down to normal again.

I don't know if the very low CSI you are at can have any impact on your equipment, others might have a better judgement on this.

And since you are more susceptible to pH fluctuations, you could have metals dissolving into your water during low pH periods which could create staining later on, e.g. during a SLAM when not watching your pH go up.

When running a pool with very low TA, you should consider adding borates to have another buffer system.

You are basically in a region where the TFP guidelines don't apply anymore. You're more or less on your own here, and you should dive deep into pool chemistry to really understand what you are doing.
 

reynolds357

Well-known member
Jun 14, 2013
60
Atlanta, GA
Your carbonate alkalinity is basically in equilibrium with atmospheric CO2 at pH 7.5, i.e. your pH shouldn't rise above 7.5 due to outgassing. Further continued pH rise would indicate other mechanisms like undissolved Cl2 gas produced by the SWG out-gassing. I'd be interested in your observations there.

You need to keep in mind that you have not much of a buffer system in your water. Adding 30ppm worth of CYA will for example drop your pH down to below 6.8 (from 7.5).

Not having a buffer also means that the fluctuations within your chlorination cycle will be quite significant. Creating 4ppm with your SWG will temporarily raise your pH to 8.3 until these 4ppm have been consumed again.

Adding enough bleach to get you to SLAM FC will push your pH to 8.6 (even after initially lowering it to 7.2). That might be a metal staining risk. If you corrected that during during the SLAM to 7.8 by adding MA, you'd run the risk of dropping down to pH 6.8 once FC levels are down to normal again.

I don't know if the very low CSI you are at can have any impact on your equipment, others might have a better judgement on this.

And since you are more susceptible to pH fluctuations, you could have metals dissolving into your water during low pH periods which could create staining later on, e.g. during a SLAM when not watching your pH go up.

When running a pool with very low TA, you should consider adding borates to have another buffer system.

You are basically in a region where the TFP guidelines don't apply anymore. You're more or less on your own here, and you should dive deep into pool chemistry to really understand what you are doing.
I bring borates up to 55 at opening every season. I do not have metal deposits. I never have water problems of any kind. I never have PH fluctuations. It steadily rises due to SWCG. I bring it down once a week.
 

mgtfp

Bronze Supporter
Mar 5, 2020
425
Melbourne, Australia
If you are using borates, then you are probably safe from pH fluctuations, but you didn't mention this in your posts above. And if your SWG is continuously producing chlorine then you are probably fine. But you mentioned above that you are also adding 3 gallons of LC from time to time - without borates, that would push your pH nearly to 9. So, having borates or not is a very important information in this discussion.

And I wanted to highlight that having no carbonate buffer in the pool is not TFP standard, and readers should be aware of that. There are consequences that they need to be aware of, and that general TFP guidelines don't necessarily apply anymore (e.g. "lower pH to 7.2 before SLAMming and you don't have to worry about pH during the SLAM" - in this case, borates are very important, but they are also not the standard TFP-way, they are more of an advanced add-on).

This is a very interesting discussion, don't get me wrong. But I think it should probably better happen in the deep end, as it is certainly beyond standard TFP guidelines. Readers copying this approach need to be aware of and understand the consequences. Just a few parameters different to yours, and things can go terribly wrong - e.g. plaster pool, metals in the water, no borates, etc.
 

reynolds357

Well-known member
Jun 14, 2013
60
Atlanta, GA
If you are using borates, then you are probably safe from pH fluctuations, but you didn't mention this in your posts above. And if your SWG is continuously producing chlorine then you are probably fine. But you mentioned above that you are also adding 3 gallons of LC from time to time - without borates, that would push your pH nearly to 9. So, having borates or not is a very important information in this discussion.

And I wanted to highlight that having no carbonate buffer in the pool is not TFP standard, and readers should be aware of that. There are consequences that they need to be aware of, and that general TFP guidelines don't necessarily apply anymore (e.g. "lower pH to 7.2 before SLAMming and you don't have to worry about pH during the SLAM" - in this case, borates are very important, but they are also not the standard TFP-way, they are more of an advanced add-on).

This is a very interesting discussion, don't get me wrong. But I think it should probably better happen in the deep end, as it is certainly beyond standard TFP guidelines. Readers copying this approach need to be aware of and understand the consequences. Just a few parameters different to yours, and things can go terribly wrong - e.g. plaster pool, metals in the water, no borates, etc.
Its new territory for me. Me and my buddy who owns a pool store have been discussing it for a while as well. He has even asked his chemical company and not got a great answer.
If the SWCG makes it impossible for your PH to drop, unless you add an acid in some form to water, why is maintaining TA important? He has one pool he is trying it on with no borate. No problems there either. I dont really understand why TA is important with SWCG. Maybe someone can answer it in a way I understand.
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,642
Houston, Texas
TA is relevant in any method of chlorination as it helps regulate fluctuations in pH. Every pool has its own "sweet spot" were the TA value keeps pH fairly stable. A lot of other factors play into pH rise and fall and the unique conditions of an individual pool determine how much influence these factors have on pH. Your pool may operate best with a low TA level. The only way to know for sure is to keep a log of test results so you can compare trends over time and see how variations in temperature and chemical levels affect your pH.
You do want to keep an eye on the pH and make sure it doesn't go too low, especially over winter when the SWG is not running. Low pH levels can damage the vinyl liner, causing horizontal wrinkles on the pool walls.
 

mgtfp

Bronze Supporter
Mar 5, 2020
425
Melbourne, Australia
It is one thing that the pool is operating fine under normal conditions while the SWG is just constantly chugging along, keeping everything in it's sweet spot. But there are other things to consider. Even simple things like adding CYA will bring pH significantly down without a stable buffer system. And then you have to consider what to do when things go wrong. As mentioned above, adding significant amounts of bleach will have an effect on pH that is no longer neglectable without a buffer system, you'll get fluctuations. Many won't even realize that their pH is out of control, because anything above 8 or 8.2 just shows up with the same colour. And if it's during a SLAM, you have to consider the interference of the pH-test with high FC.

I would strongly advise against very low TA without an alternative buffer system (borates). I would recommend a high quality pH-meter to be able to read high pH at high FC. And get chem geek's PoolEquations spreadsheet to be able to calculate the effects of adding more accurately.
 

reynolds357

Well-known member
Jun 14, 2013
60
Atlanta, GA
It is one thing that the pool is operating fine under normal conditions while the SWG is just constantly chugging along, keeping everything in it's sweet spot. But there are other things to consider. Even simple things like adding CYA will bring pH significantly down without a stable buffer system. And then you have to consider what to do when things go wrong. As mentioned above, adding significant amounts of bleach will have an effect on pH that is no longer neglectable without a buffer system, you'll get fluctuations. Many won't even realize that their pH is out of control, because anything above 8 or 8.2 just shows up with the same colour. And if it's during a SLAM, you have to consider the interference of the pH-test with high FC.

I would strongly advise against very low TA without an alternative buffer system (borates). I would recommend a high quality pH-meter to be able to read high pH at high FC. And get chem geek's PoolEquations spreadsheet to be able to calculate the effects of adding more accurately.
I never let PH go over 8. If I take it down to 7.2, 3 gals of bleach will bring it up to around 7.8.
I never really add straight CYA to water. When I need to raise CYA, diring swim season, I turn Chlorine Generator down to half its output and put 2 pucks trichlor in skimmer. In total, I use about 25 lbs of trichlor a year and use most of it in the spring and fall when salt cell is not in use.
 

mgtfp

Bronze Supporter
Mar 5, 2020
425
Melbourne, Australia
As long as you have borates in the pool, you will probably be fine. 30ppm of borates will limit the pH-rise from adding 3 gal of LC to about 7.8 - but without any borates, pH would rise to 8.7. If your buddy is running this experiment (without borates) in his pool, then I'd certainly be interested in the results. But as mentioned above, I would recommend the usage of a calibrated pH-meter that is capable to measure higher pH-levels, and does so also at higher FC-levels - I wouldn't go blind into that experiment. I do expect larger fluctuations compared to your case with borates. And with such a low CSI, I wouldn't run that experiment in a plaster pool. Not sure if there is an impact on vinyl or fibreglass (with gelcoat), or heaters. And I would get the metal levels tested - but if your buddy has a pool store, he should have the equipment to do that.

And I'd recommend to get chem geek's PoolEquations Spreadsheet, so you can calculate the effects of adding Bleach, CYA, Trichlor etc. on pH depending on TA, CYA and borate buffers:

Here is brief guide how to use it: