The process of lowering TA

[chiefwej]

Curious to know: does pH of 7.3-7.8 not raise TA, while pH 7.0-7.2 lowers it?

Just to be clear the addition of MA to lower pH also lowers the TA. Everything that raises pH also raises TA, with one exception....aeration. It does it by off-gassing. And it works best if you maintain a low pH. Even if you don't actively aerate, but do maintain a lower pH (7.0-7.2) you will have some off-gassing that will slowly raise pH, without raising the TA. So over time if you maintain lower pH the TA will go down. But no, high pH will not cause the TA to go up, it will result in scale forming if you have high CH and will keep the TA from going down, since the off-gassing only happens at lower pH. So you need to maintain a lower pH until the desired TA is reached. Aeration just speeds up the process.

 

[ptbrunet]

My long term goal is to reduce the need to add MA, more specifically to reduce the number of days between re-adding. This is so I can go on vacation or a business trip for more than a week. So my short term goal is to add borates which supposedly will reduce my need to add MA. The first part of that process is to reduce TA to 80. Is adding borates the right solution? (I won't be adding a pool cover.) So far this summer I've added water for 1.5 hours about every 2.5 weeks. I don't mind having to reduce TA once in a while; again the concern is the time between treatments.

 

[ptbrunet]

At what pH levels above 7.2 is aeration ineffective (if any)? For example, since I ran out of MA I'm aerating today at pH 7.7. Am I wasting pump/electricity cost and evaporation / refill water / refill TA cost?

Is pH from 7.0 to 7.2 safe to swim in?

 

[Richard320]

At what pH levels above 7.2 is aeration ineffective (if any)? For example, since I ran out of MA I'm aerating today at pH 7.7. Am I wasting pump/electricity cost and evaporation / refill water / refill TA cost?

Is pH from 7.0 to 7.2 safe to swim in?

Stop! You are wasting electricity.

Aeration DOES NOT lower TA. Aeration raises pH.

Acid lowers pH and TA. Aeration raises the pH back up so you can add acid again. At this point, running the pump and aerating is doing nothing for you but raising pH out of the eye-comfort zone and possibly into the positive CSI/scaling zone.

 

[ping]

Is pH from 7.0 to 7.2 safe to swim in?

Yes, it is safe to swim with the pH anywhere in the sevens. If you notice some irritation then note the pH and avoid swimming until the pH rises. You should be fine though with the pH in the sevens.

 

[JasonLion]

Aeration raises the PH more quickly when PH is low, more slowly when PH is high. Similarly, aeration raises the PH quickly when TA is high, and slowly when TA is low. Aeration will continue to work, though sometimes very slowly, when PH and TA are anywhere in the normal swimming pool range. To move the process along as quickly as possible you want the PH as low as practical. Swimming is fine when PH is down as low as 7.2. The pool is fine, though swimming not so much, when the PH is down to 7.0. PH below 7.0 can damage the pool (though only very slowly when near 7.0, more quickly the lower the PH).

 

[ptbrunet]

Acid lowers pH and TA. Aeration raises the pH back up so you can add acid again.

Thanks. That was very helpful.

 

[ptbrunet]

Added 1 gal MA today; pH dropped from 7.8 to 7.2; TA dropped from 110 (measured a couple weeks ago) to 70 (measured it twice). Now just need to aerate when I get a chance in order to raise my pH up to 7.5. Then on to step 4 of the borate process.

This went better than I expected.

Thanks for all the help!

 

[ptbrunet]

The borate process starts by lowering the TA to 70-80. Once 50 ppm is attained can the TA be allowed to go to 90+ as indicated on the calculator?

 

[ping]

The TA buffers the pH and when the TA gets high the pH will rise faster than if the TA is lower. You have to watch that you don't go too low also.

I left my TA alone for the most part since spring and it stayed in the 90 range until recently when we removed the cover and started to have to replace a good amount of water due to evaporation. The TA rose to 110 and I just finished lowering it back down to 70. When my TA was at 90 I would have to add acid once a week to control the pH between 7.5-7.8 range. When I had to add acid twice in one week I knew something was different and it was the TA that rose to 110. If you are happy with the rate the pH rises then leave it alone. If the pH is rising too fast for you, lower the pH back down to 70 and see if that helps.

 

[chem geek]

The borate process starts by lowering the TA to 70-80. Once 50 ppm is attained can the TA be allowed to go to 90+ as indicated on the calculator?

If you are getting the 90+ from balancing the CSI, you can do that by targeting a somewhat higher pH level such as 7.7 or 7.8 instead of 7.5. At a pH of 7.5, the 50 ppm borates only add 5 ppm to TA. Even at pH 7.8, 50 ppm borates contribute around 10 ppm to TA.

 

[ptbrunet]

After dropping my TA to 70 with a pH of 7.2 it took 3 days, including one 1.5 hour session of aeration to raise the pH up to 7.4. Adding borax tomorrow.

 

[chiefwej]

Per the Pool Calculator assuming you currently have zero borates, you'll need 12 boxes of borax (add 11.6) and 3.3 gallons of 31% MA. Add about half of the borax then add about half of he acid, then repeat. In the end check the pH and use just a bit more acid or borax as needed to get the pH right.

 

[ptbrunet]

Added 11.5 boxes of borax and 3.5 gal of MA, half of all that at a time, brushing after the addition of each half. In order to get better distribution, the pump was on the high speed setting I use when running my skimmers. After all that the pH was 7.3. I'll wait 2 days with the pump running on its normal low speed setting and then measure my borate and pH levels again and make any final adjustments. Dumping the borax into a skimmer was a good way to add borax. That way I could break up any clumps of borax that were at the bottom of the basket.

The process took about 1.75 hours from start to finish.

 

[chiefwej]

You should notice that your pH is more stable. Mine holds steady for up to a week before I see a perceptible rise and add acid to bring it back. You may also see some extra sparkle in the water.

 

[ptbrunet]

Hi chiefwej, I was getting a little over a week between the 7.4/7.5 to 7.8 rise so I'm hoping for at least a couple weeks between additions. I'd like to be able to go out of town for at least up to 16 days.

The pool might be a little cleaner looking. It's not really perceptible. It was pretty clear before - thanks to TFP and BBB.

 

[ptbrunet]

Hi chiefwej, The sparkle appears to be noticeable when there is turbulence, in the streaks where the rays of sun are amplified.

 

[chiefwej]

Glad you're happy with the results.

Cheers,

 

[Jimchap]

Five days ago, my TA was 240 and Ph was 7.0. I couldn't drive the TA down without driving down the Ph, and couldn't increase the Ph without driving up the TA. 24K gallon plaster pool wouldn't hold a chlorine level and green algae was sprouting. Reading about aeration on the Web, I purchased a Rigid brand vacuum (because I read it has a life-time motor guarantee) at Home Depot, 6.5 hp with blower attachment ($120), and aerated the pool during the day, and added one gallon of Muriatic acid ($8/gal at hardware store) in columns in still water each night. TA came down 20 -30 each day. Ph went to 7.0 after each acid treatment but came up to about 7.3 each day after aeration. I strapped the blower to a heavy umbrella stand and tied the air hose to a board sticking out several feet into the pool, with a divers' weight belt strapped to the air hose; its almost too powerful. Water is splashing everywhere. Also ran the attached spa in fill mode with drain closed and jets on, so it overflows into the pool. I've been running the spa and blower each day. Now TA is down to 120 and the Ph is about 7.4. The aeration process works like magic to raise Ph, it just takes a little time.

 

[chem geek]

Welcome to TFP!

Thank you for sharing your successful story. Though those of us who believe in science (physics and chemistry) understand how the process works and have faith in it. Unfortunately, the pool industry continues to tout incorrect methods such as the acid column aka slug method or they believe that adding the acid slowly vs. quickly makes a difference, etc. Very few pool service people and pool store employees know the proper way to lower TA through a process of acid addition and aeration at low (but not too low) pH as described in the Pool School article on how to Lower Total Alkalinity. This method, at least for pools, may have been first described by Ben Powell sometime before 2004 (at PoolSolutions).