Lowering TA

[Duk]

I am having to lower my TA for the first time in 9 years on this pool.
My current numbers are as follows;
FC-12 (just finished shocking a couple of days ago)
CC-0
TA- 120 (initial was 150)
CH-290
CYA~ 60-65
pH-7.2
Borates-45
salt-3100
plaster pool (21,500 gal), SWG
I've never had to lower my TA here, I usually have to add baking soda monthly to maintain 80-90, so this is new to me. I assumed the TA would come down naturally but after a month it was not moving. It is my understading that TA comes down with lower pH values and moves up with a higher pH. So, how much below my target of TA=80 should I seek for when I raise the pH backto 7.7 or so? Is it advisable to continue circulating 24hr/day while at these low pH values and is it detrimental to the pool/equipment to hold thes low pH values for a few days while lowering TA?
Thanks for the advice,
Larry

 

[anonapersona]

It is my understading that TA comes down with lower pH values and moves up with a higher pH. So, how much below my target of TA=80 should I seek for when I raise the pH backto 7.7 or so? Is it advisable to continue circulating 24hr/day while at these low pH values and is it detrimental to the pool/equipment to hold thes low pH values for a few days while lowering TA?
Thanks for the advice,
Larry

Let the aeration of the waterfall be what raises the pH back up to 7.7 or so, then add muriatic acid to bring it back down to 7.2. That is what lowers the TA.

 

[Duk]

Let the aeration of the waterfall be what raises the pH back up to 7.7 or so, then add muriatic acid to bring it back down to 7.2. That is what lowers the TA.

So, if I understand you correctly, I may need to perform this cycle multiple times. I guess you would check your TA each time you bring your pH back up to 7.7 (by aeration) or so to see where I'm at? Is it a problem to be at this lower pH for a day or so?
Thanks,
Larry

 

[dmanb2b]

The addition of muratic acid lowers TA. Aeration raises PH without affecting TA. I know TA of 120 is not optimal, but are you experiencing frequent PH rise? If not, there is no rush to lower TA, especially if in the past you say your TA has naturally fallen over time. Higher TA promotes PH rise.

 

[anonapersona]

pH at 7.2 is not supposed to be a problem. I am lowering TA in my pool now and we swam at pH of 7.3 and my husband said it stung his eyes a bit, just a bit. TA was 140 at the start of May and is 80 now. So every few days when pH gets back up to 7.8 I drive it down to 7.2. My pH is constantly rising due to the spillover spa and waterfall. My fill water has TA of 350 and so anytime I add water I am raising the TA a lot. And twice this month I wandered off while topping off the pool so I really messed with the numbers that way. So keeping TA down and watching pH is a constant thing for me.

So, yes, the procedure is to use MA to run pH down to 7.2 which also lowers TA, then circulate and aerate as much as possible to get the pH to raise up but TA will stay lowered. Then check what TA is before adding MA again so you don't add too much for the new values.

Using Pool Calculator for my pool volume, at TA 120, I need 62 oz of MA to lower pH from 7.7 to 7.2, but when TA is down to 80, that same pH change takes only 43 oz of MA.

 

[Duk]

The addition of muratic acid lowers TA. Aeration raises PH without affecting TA. I know TA of 120 is not optimal, but are you experiencing frequent PH rise? If not, there is no rush to lower TA, especially if in the past you say your TA has naturally fallen over time. Higher TA promotes PH rise.

yes, my pH is is always rising. I use a minimum of 48 oz. of MA/wk. I have not checked my fill water this year, but it seems something has changed as the TA does not fall as it used to. I normally have to add 5-6# of baking soda per month. I'm running the water falls and circulating now to raise the pH to 7.7 or so. I will test again in the morning. It seems to take alot of MA now with the borates.
Thanks for the help,
Larry

 

[dmanb2b]

Anytime Larry...yeah, borates have that effect. It will take more MA to lower PH, if you have borates at 50ppm. Since you are experiencing that much PH rise, you can target TA of 60-70. You'll get there

 

[anonapersona]

Anytime Larry...yeah, borates have that effect. It will take more MA to lower PH, if you have borates at 50ppm. Since you are experiencing that much PH rise, you can target TA of 60-70. You'll get there

So, would that be good advice for me as well? I do not have borates but I am always dealing with the pH rise. I've never tried to get TA below 80 before. Should I try for 60?

 

[JasonLion]

The first thing to try is to either lower TA to 60 or let it drift down to 60 by it's self. Borates can also help, however borates is more work/money, so not the first thing to try.

 

[Duk]

Update; After running the water falls and circulating for approx. 8-1/2 hrs. the ph is 7.6 and TA is 100. My plan is to lower the pH at least one more time to 7.2 and aerate back to 7.6-7.7. Slow progress.
Larry