High TA in Salt Water Pool

[Oskee2004]

I have very high TA and can't seem to knock it down. Here's some background.

This is year 3 with our pool, but its 10 years old - we moved in late summer of 2019, so just the 2nd year of opening and full season. The previous owners had a Hayward SWG installed, but they turned it off a couple years ago. I had a new cell installed and turned it back on for use this year (there was already enough salt in the water from previous use)... just including that background in case it matters.

I noticed the alkalinity was high late last season, after noticing high pH that kept drifting. We were more or less done for the year, so I didn't do anything about it and figured I'd address it after I opened it this year. We opened the pool about a week ago, and its in great shape... other than pH and TA. The pH was >8.0 a few days after we opened it and TA was 225. I used the pool math calculator and added muriatic acid to drop the pH to 7.0. We have a slide that I figured would aerate the water and expected some rain (it didn't come). A couple days later, pH was back up to 7.6 and TA was 200. I added more muriatic acid to drop pH to 7.0. Today, pH is 7.4 and TA is still 225. I'm wondering if I'm not aerating enough? I'd appreciate any advice. Here are the other numbers:

40,000 gallon pool
FC = 17 (I know that's high. They put 8 gallons of liquid chlorine in when they opened the pool last week - its been very cool here and I had the SWG running... I turned it off this morning until the FC drops)
CC = <0.5
pH = 7.4
TA = 225
I forgot to write down the CYA but it was somewhere around 80.

 

[cowboycasey]

The first thing to know is you can not test PH with chlorine over 10, It will read high.. so turn off your SWG and wait till FC is below 10...

TA takes time to go down, like weeks of time.. You can make it faster by running a sprinkler system connected to a return or point the returns up to make waves in the pool water... your slide will also help... Every time you drop PH it drops TA so the faster you can have PH rise the faster the TA will go down..

What is the TA of your fill water? if it is high this is going to be an ongoing battle..

Also, the TA should not be going from 200 to 225 unless your fill water is high or there is a testing error..

 

[Oskee2004]

The first thing to know is you can not test PH with chlorine over 10, It will read high.. so turn off your SWG and wait till FC is below 10...

TA takes time to go down, like weeks of time.. You can make it faster by running a sprinkler system connected to a return or point the returns up to make waves in the pool water... your slide will also help... Every time you drop PH it drops TA so the faster you can have PH rise the faster the TA will go down..

What is the TA of your fill water? if it is high this is going to be an ongoing battle..

Also, the TA should not be going from 200 to 225 unless your fill water is high or there is a testing error..

Thanks. That's very helpful. I'm guessing difference from 200 to 225 is testing error, because I haven't added any water. I'll give it time.

 

[Andrew_D]

I noticed in Water Balance for SWGs - Trouble Free Pool that recommended TA is 60-80 and it stresses the importance of this. I'm wondering if I will have issues with my new SWG this season as well as my fill water has TA of around 400-600. Last year, I had it down to about 200 by the end of the season and then because of our slightly frigid winters (ha!) the pool was drained. So I don't think I will ever be able to achieve the recommended TA level.

Andrew

 

[mknauss]

I'm wondering if I will have issues with my new SWG this season

The reason it has an importance on a lower TA with a SWCG is due to scaling on the cell plates. If you cannot get your TA down to those levels, then you need manage using CSI (Calcium Saturation Index) which is calculated with the Poolmath app. You will need to manage pH and possibly CH to maintain a CSI of -0.3 to 0.0 to keep the SWCG from creating scale.

 

[Andrew_D]

The reason it has an importance on a lower TA with a SWCG is due to scaling on the cell plates. If you cannot get your TA down to those levels, then you need manage using CSI (Calcium Saturation Index) which is calculated with the Poolmath app. You will need to manage pH and possibly CH to maintain a CSI of -0.3 to 0.0 to keep the SWCG from creating scale.

Interesting. I have more reading to do!

Andrew

 

[Andrew_D]

The reason it has an importance on a lower TA with a SWCG is due to scaling on the cell plates. If you cannot get your TA down to those levels, then you need manage using CSI (Calcium Saturation Index) which is calculated with the Poolmath app. You will need to manage pH and possibly CH to maintain a CSI of -0.3 to 0.0 to keep the SWCG from creating scale.

Last year my CH was consistently 100-125. pH constantly rising. Most likely due to the high TA. Then I'd add muriatic acid and lower the pH. Agitation would rise pH and lower TA. Process continues. However, starting with TA of 500.... it takes a while! In fact, by the end of the season, when the time came to drain my pool, TA was 200. That's as low as I got it.

I played around in poolmath and right now, it seems like it is a non issue because the water is only 40-45ºF. TA and pH changes don't seem to do too much. However, when I use temps of 80-85ºF which is where we swim at, pH changes are a huge factor. I guess this means I will have to keep a closer eye on pH to keep it in the sweet spot.

Would I be correct in assuming not to worry too much about lowering TA? I can't get it low enough anyway... I just don't have enough season! Would I be better monitoring pH and CSI and trying to keep them in line? (Obviously, I'm still going to run all the tests!)

Am I better to keep my CYA closer to the lower end of the ideal range (60-70) or higher end (80-90) for SWG?

Or should I remove the cell and inspect/clean in acid more frequently?

Andrew

 

[mknauss]

Would I be correct in assuming not to worry too much about lowering TA?

Only thing I can say there, is that in my pool, the TA has a dramatic effect on the scale in the SWCG. You will have to see if your system can have a really elevated TA.
I would suggest running a lower CYA in your climate. Try 50 ppm. One, it helps a little with CSI. Two, you really do not get the UV impact we do farther south.
Try to NOT clean the cell with acid. Each time you do, it significantly decreases the life of the cell.

 

[Oskee2004]

I would say do as much learning about the chemistry concepts as possible (which you're doing), and listen to the advice from guys like Marty and cowboycasey. Those guys have all of this stuff pretty locked down and are very generous with their support/advice.

I got creative and put put a pump on my steps (so I wouldn't take any risks with the liner), hooked the hose up to a sprinkler, then clamped it to the ladder at an angle to create a spa effect... hopefully that speeds up the process!

 

[Rodex]

The reason it has an importance on a lower TA with a SWCG is due to scaling on the cell plates. If you cannot get your TA down to those levels, then you need manage using CSI (Calcium Saturation Index) which is calculated with the Poolmath app. You will need to manage pH and possibly CH to maintain a CSI of -0.3 to 0.0 to keep the SWCG from creating scale.

My TA is consistently between 90-110. I just installed a SWCG. I searched for high TA and I’m nowhere near some of the high levels, so I could probably lower it pretty fast - but in general is a little bit on the high end much of a concern? I’m -0.33 CSI right now, and increasing my CH to 350 should bring me to -0.14.

 

[mknauss]

but in general is a little bit on the high end much of a concern?

You will find out. Every pool water is different. Test and monitor.

 

[DeanP66]

You might try a home made aerator like this one.

pancakes wilmington nc

You can attach it to a return line or even to a submersible pump. I originally used it like in the picture, connected to where my polaris pressure side cleaner would attach. However, I decided to go with a submersible pump instead because it used way less electricity than my booster pump for the Polaris. IMO, a slide doesn't seem like it would generate very much turbulence on the water, so maybe that's why you're not seeing your pH climb up fast enough.

 

[Andrew_D]

Only thing I can say there, is that in my pool, the TA has a dramatic effect on the scale in the SWCG. You will have to see if your system can have a really elevated TA.
I would suggest running a lower CYA in your climate. Try 50 ppm. One, it helps a little with CSI. Two, you really do not get the UV impact we do farther south.
Try to NOT clean the cell with acid. Each time you do, it significantly decreases the life of the cell.

OK. Water was at CYA 50 yesterday when I tested. I'll try to keep it there.

Gotcha on the cleaning. I think I'll try some more aggressive aeration to try to lower the TA faster. Sounds like getting it lowered, while watching pH, is my best bet.

I would say do as much learning about the chemistry concepts as possible (which you're doing), and listen to the advice from guys like Marty and cowboycasey. Those guys have all of this stuff pretty locked down and are very generous with their support/advice.

I got creative and put put a pump on my steps (so I wouldn't take any risks with the liner), hooked the hose up to a sprinkler, then clamped it to the ladder at an angle to create a spa effect... hopefully that speeds up the process!

Definitely some knowledgeable folks on here! Just discovered this site last year and it made a huge difference!

The kids are wanting some water features, so once I get those set up it should speed up the aerating!

Andrew

 

[Oskee2004]

You might try a home made aerator like this one.

pancakes wilmington nc

You can attach it to a return line or even to a submersible pump. I originally used it like in the picture, connected to where my polaris pressure side cleaner would attach. However, I decided to go with a submersible pump instead because it used way less electricity than my booster pump for the Polaris. IMO, a slide doesn't seem like it would generate very much turbulence on the water, so maybe that's why you're not seeing your pH climb up fast enough.

Thanks! I rigged up something similar a few days ago, but not nearly as elaborate (just PVC connected to return that bubbles just over top of the water like a small fountain). Seems to be doing the job, slowly... I was down to 200, then 175, and 150 this morning (testing with Taylor kit under the "expected high TA" method, so everything is rounded to 25's). We also got a good rain storm on Wednesday night, so I'm sure that helped. Progress!

 

[Oskee2004]

Just posting an update... been almost a month and my TA is down to 95 (Taylor test was dark pink at 90 and bright red at 100). Definitely seems like decent rain was the most effective at bringing it down. I put together a simple aerator tube attached to my return jet, but its progress was very very limited. I kept an eye on the weather and brought pH down before a solid rain. That seemed to consistently bring TA down 20-40 points each time. Still been a bit cold here for much fun. So, kids splashing around would probably do the trick as well.