The process of lowering TA

[ptbrunet]

I hope this hasn't been answered before - didn't have time to look through everything...

I use bleach. My TA is 110, CYA 45, measured by my TF100 kit. I need to lower my TA to 80, but is that 80 as read via my kit or do I need to subtract the 30% TA due to my CYA from either the 80 and/or 110 values? I'm guessing I need to drop by 30 but want to be sure.

How long will I need to aerate to lower my TA? I have one bubbler which does expose quite a bit of water and three water jets (about a half inch opening on the nozzles). If it matters it's around 100 during the day at this point.

 

[chem geek]

Re: So you want to add borates to your pool--Why and How

It's the TA measured in your kit. We never use the "adjusted TA" directly. It's handled automatically in calculators such as The Pool Calculator when it calculates the Calcite Saturation Index (CSI).

As for how long it takes to lower the TA, that is hard to predict. It goes faster if you have more aeration and keep the pH low by adding acid. The TA will drop faster when it is high and more slowly as it gets lower.

 

[ptbrunet]

How low should I drop my pH? Will 7.5 be enough? Is there any problem if I do this over several days? I'm guessing that I won't want to drop my pH below 7.5 if it's going to take me several days to get the TA down.

I'm interesting in any other's experience on how long it took them to drop TA by 30 (110 to 80 in my case). My pool is 15K gallons.

 

[JasonLion]

Re: Lower my TA to 80, but is that 80 as read via my kit or

If you are tying to lower TA, lower the PH to between 7.0 and 7.2 each time, it will go way more quickly that way.

 

[chiefwej]

Re: Lower my TA to 80, but is that 80 as read via my kit or

I ran my fountain and the pump in my spa (without heat naturally) 24/7 for a couple days and went through 3 gallons of acid to get mine down. Your time will vary depending on several factors.

 

[ptbrunet]

The noise from the water features drives my wife crazy after about 30 min. Does TA eventually drop over time? Maybe I just need to wait it out.

My goal is to reduce the use of MA so I could leave town for longer than a week. After about a week my pH rises from 7.5 to 7.8 and I have to add more MA. Any other ideas (other than adding an MA pump)?

 

[chem geek]

Re: Lower my TA to 80, but is that 80 as read via my kit or

If your pH tends to rise and you add acid to lower it, then this lowers the TA as well so over time the TA may drop. However, there is TA in the fill water so if you have evaporation and refill then the TA may rise over time. Which one wins out depends on the amount of each.

 

[ptbrunet]

Guess I'll add MA and aerate every time I'm "home alone"

If I drop it down to 7.0 and then aerate for a while I assume I have to get the pH back to 7.5 until the next time I can aerate. I see I can use washing soda, soda ash, or borax. Does it matter which one I use considering I'm trying to lower TA over time?

 

[chem geek]

Re: Lower my TA to 80, but is that 80 as read via my kit or

No, you aerate the entire time and just keep adding acid to have the pH low. You don't need to wait for the pH to rise to 7.5 -- if you keep it lower at 7.0 to 7.2 the entire time, the process will go faster. What you are doing is trying to drive out carbon dioxide from the water and both aeration and pH help do that more quickly.

 

[ptbrunet]

The point I was getting at is that since I won't be able to aerate continuously, i.e. 24 hours a day for a couple of days, I'll have to break that period up into a couple of hours at a time separated by several days. So can I leave my pH at 7.2 during the separation days or should I raise it back up to 7.5 each time?

 

[ping]

Re: Lower my TA to 80, but is that 80 as read via my kit or

You do not add chemicals to raise the pH as they will make the TA rise also to some degree. Aeration raises the pH and leaves the TA alone.

Another way that you can lower the TA is do what I just went through, I lowered my TA from 110 to 70 in a months time. Instead of actively lowering the pH and aerating, I lowered the pH to 7.2 once it hit 7.6, and in a month it has lowered to 70. I don't have high TA fill water, but it is high enough that it rises slowly over time.

 

[ptbrunet]

Thanks, Sounds like a good plan. So I'll do two separate things:

1) Aerate when I can
2) When pH gets to 7.6, lower it to 7.2.

 

[Patrick_B]

The point I was getting at is that since I won't be able to aerate continuously, i.e. 24 hours a day for a couple of days, I'll have to break that period up into a couple of hours at a time separated by several days. So can I leave my pH at 7.2 during the separation days or should I raise it back up to 7.5 each time?

That is Ok, just aerate as much and as often as you can. Lowering TA takes time in most every case depending on a few factors, but your plan will work fine.

 

[Richard320]

Question: Why are you worrying about it? Are you having to add acid every other day or something? Do you have super-high CH that puts you at risk of scaling? If neither applies, who cares? As it says in the article in Pool School,

You shouldn't lower TA just to reach a target number. Make sure you actually have one of the above issues before lowering your TA.

 

[ptbrunet]

Hi Richard, I want to add borates so I don't have add MA once a week. In order to add borates I'm supposed to have TA of 70-80.

 

[ptbrunet]

My pool takes about 9 oz MA to lower pH by 1. A gallon will drop 7.8 to 7.1. So I'm thinking I'd add a gallon every time it gets to 7.8. That way I won't have to deal with pouring/measuring MA (not my favorite task). It should take about 2 weeks to rise back up from 7.1 to 7.8. Would that work OK?

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

 

[duraleigh]

My pool takes about 9 oz MA to lower pH by 1. A gallon will drop 7.8 to 7.1. So I'm thinking I'd add a gallon every time it gets to 7.8. That way I won't have to deal with pouring/measuring MA (not my favorite task). It should take about 2 weeks to rise back up from 7.1 to 7.8. Would that work OK?

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

That will work fine. I do not understand your last question...pH neither lowers or raises TA.

 

[ptbrunet]

Hi Dave, See ping's note above. Maybe it's the MA that does it.

 

[ptbrunet]

My city water report shows that my TA ranges from 134-236 with an average of 185. With the high central TX temps and the aeration looks like I'll be adding some in as I compensate for the evaporation.

 

[chem geek]

With that high TA in the fill water, your pool is going to be requiring acid addition unless you significantly reduce evaporation by using a pool cover. Otherwise, evaporation and refill will increase TA over time.