Reducing alkalinity question

[mrluckies]

I need to reduce my alkalinity from 150 down to about 70-90 for a salt water in ground pool. According to pool math, it says to decrease pH to 7.2 and then raise the pH by aerating the water. My pH was already at 7.2 from opening it and the alkalinity only dropped from 150 to 130 in a week, which may also have been from the heavy rains we had last week. So my question is what causes the alkalinity to drop?

Do I need to start at a pH of 7.5 and drop it to 7.2 in order to get the alkalinity to drop?

Or is it being at 7.2 pH that causes it to drop?

Or is it the aeration that causes the alkalinity to drop?

I usually don’t worry much about alkalinity but I’m usually only around 100, even though it probably should be 70-90. My pH doesn’t change too much so I’m not too worried about it usually. However at the end of last season I had a new liner put in and had to refill and my water chemistry is way off from where it usually is.

I’ve got my cya at 70 and hardness is only around 150, but it’s a vinyl inground pool. I use a Hayward salt cell system. Water temp is about 80 and the pool gets sun nj sun almost all day.

 

[Toxophilite]

Yes, I just lower pH and aerate according to Pool Math. TA will keep falling but may take awhile. I started at 120 at beginning of March and just now in 80 range, but, I also had new plaster adding to the problem.

 

[ajw22]

You need to let the pH rise to 8 then drop it around 7.2 to reduce the TA. That large reduction of pH with acid reduces the TA also. Then raise the pH with aeration and repeat.

TA - Further Reading

www.troublefreepool.com

 

[pjt]

So my question is what causes the alkalinity to drop?

Adding Muriatic acid (MA).

Do I need to start at a pH of 7.5 and drop it to 7.2 in order to get the alkalinity to drop?

No.

Or is it being at 7.2 pH that causes it to drop?

No.

Or is it the aeration that causes the alkalinity to drop?

No. Aeration will speed up pH rise without affecting TA. After the pH rises, add MA which will lower both the pH and TA.

 

[mrluckies]

Ok thx for the clarification! I’ve been doing it wrong the last couple years and wondering why it didn’t drop.

What’s the best way to aerate the pool? I have four return jets. I assume I just point them up so the break the surface of the water? Any other tips for aerating?

 

[ajw22]

? Any other tips for aerating?

Aeration - Further Reading

www.troublefreepool.com

 

[Mikey0214]

Yes, I just lower pH and aerate according to Pool Math. TA will keep falling but may take awhile. I started at 120 at beginning of March and just now in 80 range, but, I also had new plaster adding to the problem.

What’s your trick on measuring and adding MA to your new plaster pool to reduce the PH?

Pool company added MA on Tuesday for me and it dropped the TA and the PH. Today my PH was at a 7.8 so I may have to add MA tomorrow for the first time by myself depending on where the PH test comes back at.

 

[Toxophilite]

What’s your trick on measuring and adding MA to your new plaster pool to reduce the PH?

Pool company added MA on Tuesday for me and it dropped the TA and the PH. Today my PH was at a 7.8 so I may have to add MA tomorrow for the first time by myself depending on where the PH test comes back at.

For measure, I have a long-snouted, 28oz, pitcher type, measuring cup that I can pour in front of a deep end return jet using a tiny stream of MA. For amount, I already know from experience how much one pitcher full will adjust. You have to learn your individual pool and how it reacts. You can start learning for your pool by getting the Pool Math app. Keep a log. Add doses in 1/2 increments to make sure your inputs and outputs are working, and later you will intuitively know movements better than a calculator can predict.

When I see it getting to the 7.8 like you are now, I know after one more day it will need MA. One 28oz pitcher takes me down to 7.5 again. I usually leave it there for next run up to 8.0. For your size pool, I would add about that much now and test after about 15 minutes. That will start to give you a baseline of how much moves what on the number scale. You will probably need more to get lower, but it's better to start in increments at first.

 

[Mikey0214]

For measure, I have a long-snouted, 28oz, pitcher type, measuring cup that I can pour in front of a deep end return jet using a tiny stream of MA. For amount, I already know from experience how much one pitcher full will adjust. You have to learn your individual pool and how it reacts. You can start learning for your pool by getting the Pool Math app. Keep a log. Add doses in 1/2 increments to make sure your inputs and outputs are working, and later you will intuitively know movements better than a calculator can predict.

When I see it getting to the 7.8 like you are now, I know after one more day it will need MA. One 28oz pitcher takes me down to 7.5 again. I usually leave it there for next run up to 8.0. For your size pool, I would add about that much now and test after about 15 minutes. That will start to give you a baseline of how much moves what on the number scale. You will probably need more to get lower, but it's better to start in increments at first.

Just saw your reply. I appreciate the help! I Tested my PH this morning and it came back at 8.0. Pool math told me to add about a 1/4 of a gallon to get it down to 7.2. I did what I thought was about a quarter of a gallon and it was dead on. Brought it down to 7.2.

Do you mind sharing a picture of the pitcher you use and do you remember where you got it from ?

Thanks in advance.

 

[PoolStored]

Here is another thread on aerating that is recent and might help:

Aerating

Hello, Last year I struggled a little bit with aeration. We have a 14000 gallon above ground pool at 24' round. With that being said there were times I needed to lower TA. I believe I read baking soda was a bad method as I think I remember people saying it can cause cloudy water. With that said...

www.troublefreepool.com

 

[mrluckies]

Just out of curiosity, can I use washing soda to raise pH or will that also mess with other things?

I built an aerator using soaker hose like mentioned in the article, but then found I have a container of washing soda (pH up) and wasn’t sure if I could use that at all.

 

[proavia]

For measure, I have a long-snouted, 28oz, pitcher type, measuring cup that I can pour in front of a deep end return jet using a tiny stream of MA. For amount, I already know from experience how much one pitcher full will adjust. You have to learn your individual pool and how it reacts. You can start learning for your pool by getting the Pool Math app. Keep a log. Add doses in 1/2 increments to make sure your inputs and outputs are working, and later you will intuitively know movements better than a calculator can predict.

When I see it getting to the 7.8 like you are now, I know after one more day it will need MA. One 28oz pitcher takes me down to 7.5 again. I usually leave it there for next run up to 8.0. For your size pool, I would add about that much now and test after about 15 minutes. That will start to give you a baseline of how much moves what on the number scale. You will probably need more to get lower, but it's better to start in increments at first.

It is best not to transfer MA into a pitcher. Use it straight out of the jug it comes in. Undershooting or overshooting slightly won't make a big difference. Anytime you transfer liquid MA or chlorine there is a chance of splashing or spilling the liquid where you don't want it. After a few tries, you can usually pour within a few ounces of the needed amount using the free pour method. If you are intent on using a separate container, do it only over the pool and as close to the water as you can get.

Also, no need to dilute prior to addition.

 

[ajw22]

Just out of curiosity, can I use washing soda to raise pH or will that also mess with other things?

I built an aerator using soaker hose like mentioned in the article, but then found I have a container of washing soda (pH up) and wasn’t sure if I could use that at all.

Washing soda will also raise your TA with your pH. Aeration will not.

If your TA is good or you are trying to lower it then aeration is the way to go.

• Baking Soda = big TA change, small pH change
• Borax = big pH change, small TA change
• Soda Ash/Washing Soda = big pH change, big TA change.