To lower TA with MA, does the rate of pH rise afterward matter?

[HouTX]

My current TA level is 75 and I am trying to get it near 60 to help better manage pH which drifts up. 10 days ago I lowered pH from 8 to just above 7 using MA. However, I did not use aeration afterward and let the pH drift upward gradually as it tends to do in my pool. When I checked my TA a week later it is still at 75. Two questions:

1. Does the pH have to be raised rapidly from 7 for it to lower TA ?
2. Does any addition of MA reduce TA, or only when pH goes below a certain number ?

Current readings are as follows:

pH 7.6
FC 3.5
CYA 65-70
TA-75
CH-350

 

[Richard320]

It's a fixed amount of TA reduction based on the amount of acid. Aeration just speeds the pH rise so you can add acid again sooner. Just plug all your numbers into poolmath so it tells you how much acid to get to 7.2 pH and then scroll down to Effects Of Adding Chemicals and input that acid dose and you'll get a pretty close approximation of how much your TA will lower with the pH adjustment.

 

[woodyp]

You do realize that waterfall and SWG and spillover spa all have a lot to do with your PH rising when you run them. I doubt 60 TA is gonna overcome that.

 

[HouTX]

I have gone through 2+ gallons of MA in the last two months and my TA has remained at 75. That does not coincide with what I have read, or with PoolMath

- - - Updated - - -

Yes I do understand that and I was hoping that a TA of 60 would buffer pH better under the circumstances.

 

[Richard320]

Test your fill water. It could be a source of TA. So could curing plaster.

 

[woodyp]

I gotta tell ya',,,,,a gallon a month for all those water features in a pool your size ain't bad!

 

[HouTX]

There is no curing plaster, and due to the recent rains the Autofill came on this week after a long while.

 

[bkfamily1]

You do realize that waterfall and SWG and spillover spa all have a lot to do with your PH rising when you run them. I doubt 60 TA is gonna overcome that.

ah, the beauty of a complete signature to evaluate issues...

FYI, I have been working my TA down for about a month. I add a gallon of MA to my 30K gal IG when the pH is 7.5 or 7.6. That brings the pH down 0.3 or 0.4 and the TA down about 15 or so. Then I aerate for a couple days to bring it back up to 7.5 or 7.6. And the changes I am seeing were well-predicted by pool math.

 

[HouTX]

I was using the 10ml test which goes in .25 increments, I tried again with the 25ml sample (x.2) and I am spot on at 60, so it was a testing issue and I should have known better.

Which leads me to my next question, constant addition of MA in an SWG pool will eventually lead to a very low TA which will then to be to be addressed ?

PS: Although I have 3 "sheer descents", I am only running them 2 minutes a day to recirculate the water (pool school guy had advised 20 minutes a day). I do understand that I still have to contend with the SWG and SPA spillover but I have tweaked my MA dosage and getting close to once a week

 

[chem geek]

Every gallon of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in your 30,000 gallon pool lowers the TA by 16.7 ppm. So the TA will go down over time unless something gets added to the pool to increase it. Evaporation and refill with water that has TA and CH add both to the pool and is the most common source for rise of these two parameters. If you use a low quality chlorinating liquid or bleach with a lot of excess lye in it, then that will lead to a slow TA increase over time though you'd likely notice the larger pH rise first.