Lowering Total Alkalinity (Without Lowering pH)

[Nitro]

This topic comes up quite a bit. I explain the process in my Maintenance Guide, but I thought I'd post a separate thread for easy reference. I won't get into detail why you would want to do this here. See my guide for more info. I will say this, the key is, you should NOT focus on adjusting pH directly. Instead, you should focus on adjusting TA to an ideal level, in order to keep your pH in line. If you're using Bleach TA should be 50-60ppm, if using Dichlor TA should be 80-100 ppm and if using Bromine TA should be 100-120 ppm.

The problem with lowering Total Alkalinity (TA) is that when you add acid to lower TA, pH also decreases. This limits the amount you can lower TA without pH becoming too low. However, there is something you can do to raise pH that leaves TA alone, Aeration. Aeration is the process of turning on all the jets and air features in your tub, in order to pump as much air into the water as possible. By adding Acid and Aerating you can lower TA, while keeping pH the same.

One thing to remember is, the amount that TA decreases is directly proportional to the amount of acid you add. That is, in a 350 gal tub, 8 oz of Dry Acid will lower TA by 100ppm. It is important to know (by calculating) how much Total Acid you need to add to your tub in order to get to your Target TA.

The other thing to remember is, the higher your TA, the less effect acid will have on your pH. If your TA is high, adding acid won't effect it much. This confuses some beginners (and experts alike), which causes them to give up on lowering their pH. Because of this, you need to add more Acid in the beginning, and less as you get closer to your Target TA.

So, let's get started. Here is the process.

1. Turn on all your jets and air features and keep them on the entire process. (i.e. Aerate)
2. Calculate how much you want to lower your TA, and how much acid you need to add to lower it.
3. Add to the tub HALF (not > 1 cup nor < 1 TBS) of the amount of the remaining acid you need to add.
4. Aerate for 30min, and check TA/pH.
5. If TA > Target and pH is > 7.8, goto step 2.
6. If TA > Target and pH is < 7.6, goto step 4 one time.
7. If TA > Target and you can't get pH > 7.8 via aeration, Target too low. Stop here.
8. If TA = Target and pH is > 7.8, Target too high. Lower Target TA and goto step 2.

Example:
Your TA is 300ppm, you want to lower it to 60ppm, in a 350 gal tub.
To lower TA by 240 ppm you need to add a total of 2.4 cups (~19oz) dry acid.

Turn jets/air on.
Add 1 cup acid and Aerate 30mins.
Check TA/pH. TA=200 and pH>8.0
Add 6 oz acid and Aerate 30mins.
Check TA/pH. TA=125 and pH>8.0
Add 3 oz acid and Aerate 30mins.
Check TA/pH. TA=90 and pH>8.0
Add 2 oz acid and Aerate 30mins
Check TA/pH. TA=65 and pH=7.8
Add 1 TBS acid and Aerate 30mins
Check TA/pH. TA=60 and pH=7.6

The main thing to remember is, you add more acid in the beginning of the process, and taper off toward the end. This method will allow you to lower your TA in a matter of a few hours regardless of how high your TA is.

Lastly, safety is priority one. Be careful with any type of acid, especially Muriatic. If you're using Muriatic acid, wear rubber gloves and eye protection. Muriatic Acid is nasty stuff. Dilute all acid in a bucket of water and slowly pour mixure over a return flow, or middle of tub. Be careful not to splash. When mixing Acid and Water, always add Acid to water! NEVER ADD WATER TO ACID!!!

Happy Tubbing!  

[Hillbilly Hot Tub]

Whats you take on raising ALK without raising PH....Say a 10 ALK with a PH of 7.8.
Curious to your suggestion on this, maybe I missed it somewhere.

[Nitro]

Whats you take on raising ALK without raising PH....Say a 10 ALK with a PH of 7.8.
Curious to your suggestion on this, maybe I missed it somewhere.

To raise TA just add Baking Soda. It will raise TA, but won't raise pH very much. i.e. In a 400 gal tub, 1 oz BS will raise TA by ~11 ppm, but will only raise pH by ~0.02.

[Vinny]

To raise TA just add Baking Soda. It will raise TA, but won't raise pH very much. i.e. In a 400 gal tub, 1 oz BS will raise TA by ~11 ppm, but will only raise pH by ~0.02.

Not true!

In my 400 gallon tub I use baking soda to raise both TA and PH. I can get my TA from 80 to 120 and PH from 7.2 to 7.8 using baking soda.

In my 13,000 gallon pool - it has no effect on PH. I use borax for raising PH.

[Nitro]

Not true!

In my 400 gallon tub I use baking soda to raise both TA and PH. I can get my TA from 80 to 120 and PH from 7.2 to 7.8 using baking soda.

In my 13,000 gallon pool - it has no effect on PH. I use borax for raising PH.

Sorry Vinny, it is true. Chem Geek will confirm this.

The reason your pH rises in your hot tub and not your pool, is because Aeration causes pH to rise. When you add Baking Soda, only your TA rises. However, that ALLOWS pH to rise via aeration. The fact that it doesn't work the same in your pool confirms this fact. If there is little to no aeration, pH won't rise.

As I have said before, the only reason to raise TA, is if pH is too low and won't rise from aeration.

[Vinny]

We've had this conversation before and whenever I add baking soda my PH rises.

Besides my circ pump, my pumps only come on for 2 minutes max per day when I don't use my tub. And I don't use my tub that frequently.

I can't see how 2 minutes a day without air will cause my PH to stay at 7.8 for weeks. I use dichlor and MPS which are both adding acid to the tub's water. When I add dichlor the pumps are on for 5 minutes and with MPS for 20 minutes - again without air.

How much aeration is needed to raise the PH, keep it there and combat the effects of the dichlor and MPS? I would agree if the tub had air blowing out as well as this would be a cause for the PH to rise but IMO there's not much aeration going on in my tub.

[TubsAndCues]

Raising TA will also raise pH.  Try it in a pool or a hot tub or a bucket of water.  It's a natural side effect.

[kokanee001]

And some people wonder why sometimes us "newbies" have problems and get frustrated over trying to get our hot tubs properly balanced in all respects; even the "experts" don't always agree. I think I will just relax and not try to micromanage my water.....just get the readings reasonably close.
Heck, now I'm learning that trying to be too precise with the pH is not such a huge deal because it's gonna change anyway due to aeration when I use the tub............lol

[chem geek]

If you start with a TA of 80 ppm and a pH of 7.5 and add baking soda to raise the TA to 120 ppm, then the pH rises immediately to 7.6.  Outgassing of carbon dioxide, which occurs even without explicit aeration (though more slowly) will have the pH continue to rise.  So with larger increases in TA you do see a pH rise.  If you start out at a lower pH, then you will see a larger pH rise of around 0.15 that may look like 0.2 (say, from 7.2 to 7.4).

Of course, if one uses sodium carbonate (pH Up) instead of sodium bicarbonate (baking soda; Alkalinity Up), then the pH rise is much larger.

[Nitro]

Getting back to HHT's question, the ONLY way to raise TA, without raising pH (much), is to use Baking Soda.

[Nitro]

And some people wonder why sometimes us "newbies" have problems and get frustrated over trying to get our hot tubs properly balanced in all respects; even the "experts" don't always agree. I think I will just relax and not try to micromanage my water.....just get the readings reasonably close.
Heck, now I'm learning that trying to be too precise with the pH is not such a huge deal because it's gonna change anyway due to aeration when I use the tub............lol

Actually, the trick is to determine who the experts really are, and ignore the rest. LOL

[TubsAndCues]

Actually, the trick is to determine who the experts really are, and ignore the rest. LOL

No need to laugh at that one.  That's the most accurate thing I've ever read on this forum!

[Hillbilly Hot Tub]

You missed my point. We have many people that have a PH of 7.7-8.0 and an ALK of 10-20, we have to raise the ALK up a lot which raises the PH up a lot,(yes I use ALK up, not PH up) even without running jets ect. We see this a lot with the water in our area...High PH with no ALK reading.

Just a little adjustment is easy, and I will have to say I see a bigger increase in PH than whats being stated, but the new tubs do have many jets and newer ozone's that produce thousands of bubbles.

[chem geek]

If you see the pH rise much higher than 8.0, then the baking soda may not be quite pure (it might have some sodium carbonate in it) or some outgassing occurs almost right away.  When the pH is very high, say 9.0, bicarbonate will lower the pH, not raise it.  The "natural" pH when adding baking soda is dependent on temperature but is in the range of around 7.8 to 8.0.

The MSDS says it's 100% sodium bicarbonate, but clearly if you are seeing a larger pH rise then there's at least a little base getting added or there's outgassing (bubbling) that happens very quickly, perhaps during addition since the TA is very high locally when you are adding it (i.e. some carbon dioxide outgasses right away).  That's probably the explanation and would account for most people's experience when they add baking soda.  That would mean that the way it is mixed would make some difference.

[TubsAndCues]

If you see the pH rise much higher than 8.0, then the baking soda may not be quite pure (it might have some sodium carbonate in it) or some outgassing occurs almost right away.  When the pH is very high, say 9.0, bicarbonate will lower the pH, not raise it.  The "natural" pH when adding baking soda is dependent on temperature but is in the range of around 7.8 to 8.0.

The MSDS says it's 100% sodium bicarbonate, but clearly if you are seeing a larger pH rise then there's at least a little base getting added or there's outgassing (bubbling) that happens very quickly, perhaps during addition since the TA is very high locally when you are adding it (i.e. some carbon dioxide outgasses right away).  That's probably the explanation and would account for most people's experience when they add baking soda.  That would mean that the way it is mixed would make some difference.

Might make a difference if people stopped putting baking and other house hold products in their hot tub, too.  

Funny, you never see anyone baking a cake with TA Increaser.