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Lowering Total Alkalinity

76 posts in this topic

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.

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! :)

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Thanks for the great write-up. The relationship of pH and TA and how a high TA causes the pH to rise and how aeration plus acid addition are used in combination to lower the TA are all topics that confuse many and are counter-intuitive, yet the science behind how it all works is very clear.

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This forum is great! I have a question. Is it ok/accurate to balance at a cold water temp, as in 54 degree well water?

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This forum is great! I have a question. Is it ok/accurate to balance at a cold water temp, as in 54 degree well water?

Yes. You're probably going to need to fine tune over the course of a few days anyway. Just keep an eye on pH, and adjust TA accordingly.

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This forum is great! I have a question. Is it ok/accurate to balance at a cold water temp, as in 54 degree well water?

Yes. You're probably going to need to fine tune over the course of a few days anyway. Just keep an eye on pH, and adjust TA accordingly.

Thanks. I've got the process started. I should be up to temp tomorrow, as I have the heater on now. I let it go a few days and picked up 15 degree temp rise for free. My TA/ PH balancing has never gone very well. I may have more questions after things get up to temp.

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Hello,

I have been reading (and re-reading) this web site, and I'm switching over to the dichlor-then-bleach method after following the decontamination procedure.

My question is: My TA is 80, my PH is 8.0. So I need to lower my PH without lowering my TA right? (the opposite of this thread).

If I use muriatic acid, I will lower both, right?

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I would lower the TA until you get some pH stability. So if your TA is running high right now, then lower BOTH pH and TA by adding acid (such as Muriatic Acid, but be careful with that stuff -- you don't need very much and it's potent which is why dry acid is usually used in spas). Don't try and raise the TA after lowering the pH. Just see how your tub responds at a lower TA level. Odds are, after switching to bleach after a week or so of Dichlor that you will need a low TA of perhaps 50-60 ppm. If you still find the rate of pH rise too high, you can also use 50 ppm Borates.

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If your pH is stable and you are no longer needing to add any acid, then you can leave the TA where it is. Otherwise, if you're still adding some acid, you should probably keep the TA between 40-50 ppm so raise the TA to 50 ppm before you add any acid to lower the pH (in the future -- your pH doesn't need lowering now).

I presume that your TA dropped due to acid addition over time.

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Bit of a dilemma, brother-in-law has added pH-UP to increase his pH but in doing so his TA has jumped to beyond 300. The problem we have is that pH is still low, like only 6.8-7.0.

What can I do?

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Run the jets to aerate the water and the pH should rise. When it does, add acid which will lower both pH and TA. Keep it at. It will take a while and a lot of acid, but the TA will go down with continued aeration with acid addition.

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Feel a bit stupid here. Blame the effects of a bottle of nice wine because I misread the instructions on the TA test tablets container, I thought it said red to turn yellow instead of the other way round, so instead of having a high TA reading it was the opposite being very low. Amazing what a bit of sleep and a clear head does for you, anyway the fix was much quicker than the other way round and they are in the tub as I write.

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any idea where i can buy dry acid in a local store ????

Most local pool or spa stores will carry pH Decreaser. They offer it in different sizes. Most spa sizes are one pound. You can also find the same great products online too.

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You can use The Pool Calculator to answer your question, but basically 25-1/2 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid or 20¬ļ Baume) in 10,000 gallons lowers the TA by 10 ppm. So this is about 1-1/2 fluid ounces per 100 gallons for a 10 ppm reduction in TA.

When you use Dichlor, which is what I presume was your "granulated chlorine", that is net acidic. This is because chlorine usage/consumption is acidic so continued use of Dichlor will lower your TA, just as if you are adding acid. Every 10 ppm FC you add from Dichlor lowers the TA by 3.5 ppm and increases the CYA by 9 ppm. If your pH rises just from carbon dioxide outgassing, then the TA will drop slowly over time. If you need to add acid, it will drop more quickly. If you add a base to raise the pH, then the TA will rise slowly over time (unlikely because you probably do have carbon dioxide outgassing which is quite common in spas, especially with aeration from jets).

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Well, the first step in lowering the TA is to get the pH down to around 7.0 and start aerating so you can certainly do that if you want. It won't drop the TA by too much and at least you'll get your pH down. 8.7 sounds high enough to cause problems with scaling, especially in the heater, unless your CH level is very low.

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As a general rule titrations are done until one additional drop produces no further color change and the you don't count the drop that caused no further color change. There are a few exceptions such as the salt titration test and borate titration (which is NOT offered by Taylor), where you stop at the first color change to the desired color and do not go past.

So for your TA test if it takes 9 drops to change to a red, the 10th drop produces a brighter red,and the 11th drop does not change the color any further your result is 10 drops.

http://www.taylortec...e_slideshow.asp

Click on pool/spa in the upper left and then scroll down and see videos of how to do the different tests in the K-2006 (and some of their other kits) and also some general testing info videos.

You can view the CYA test and see what it is supposed to look like.

Finally here is some additional info on lowering TA that you might find useful. It also discusses the relationship between TA and pH.

http://www.poolspaforum.com/forum/index.php?showtopic=36290

Follow the link in the above post (to the swimming pool water chemistry section of the forum) and read.

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If your pH tends to stay high, then just add more acid and your TA will continue to get lower and at some point your pH should not rise so much. You can go down to a TA of 50 ppm if necessary. If you find your pH more stable, even if the pH settles in a little higher such as 7.7 or 7.8, then that's fine. You can then use 50 ppm Borates at that point for further pH buffering.

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What is your sanitizer level when you are testing pH? Are you using chlorine or bromine? HIgh santizer levels can cause a chemical interference with the pH test and cause it to read high when it is not.

Also, the main cause of pH rise in a tub is outgassing of CO2 from the aeration from the jets and bubblers so often a very low TA is needed along with the addition of 50 ppm borate to introduct a boric acid/borate buffer system.

OK - so I'm attempting to lower the pH with Muriatic Acid and have brought it down - it's now right around 8 - I know I need to get it to ~7.2 but now my TA is below the target of 100-120. According to the test kit I purchased - TA is at about 90

Bottom line is this, if your pH is constantly rising (from outgassing of CO2 then your TA is too high.I am not sure why you are attempting to maintain a TA of 100-120, that is WAY to high for a spa!!!! Even 90 ppm is too high in most cases in a chlorine spa and TA as low as 50 ppm in not unheard of to maintian pH stability.

If you were using MPS and organic bromine then a higher TA would be warranted since both are more net acidic than dichlor and the pH rise from increased CO2 outgassing would offset the constant acid 'additions' from these chemicals.

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There is a lot of misinformation entrenched in the industry that is NOT based on sound water chemistry TA levels are a prime example because most folk in the industry really don't understand what TA is and what it does. In a pool or spa TA is mostly carbonate alkalinity (sometimes called carbonate hardness) and is mostly in the form of bicarbonate at normal pool pH with (in equilibrium with carbonic acid, which for our intents and purposes is basically CO2 dissolved in the water. The higher the TA the higher the bicarbonate level and the higher the dissolved CO2..The higher the disoolved CO2 the faster it will outgas (even faster with the aeration from the jets and bubblers) and outgassing of CO2 is the MAIN cause of pH rise in pools and spa. However, most people in the industry don't understant this simple fact so you now know MORE about pool and spa water chemistry than most people in the industry! ;)B)

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no but if the santizer was low something could start growing in the tub and create a big chlorine demand.Never assume, TEST!

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high sanitizer levels can interfere with some other tests (it can causes false high pH readings and can bleach out the dyes in the mixed indicator in the TA test causing the color change to go from blue to yellow instead of green to red or fade the colors of the indicator in the CH test--however, the results of these two tests are still vaiid, just harder to read) but if the sanitizer is testing low and you are using an FAS-DPD test (drop counting), OTO test (color comparator with yellow color blocks), or FC test strips that turn to shaded os purple (NOT pink or red)then if they test indicated low sanitizer, it is low!

IF you are using DPD testing (color blocks on comparator or strips are shades of pink or red) then high santizer levels CAN bleach out the test if the sanitizer is high and make you think it is low.

This is why the general consensus here is to recommend the Taylor K-2006 with the FAS-DPD chlorine test or the K-2106 FAS-DPD kit for bromine. IF the sanitizer is testing low it is low (up to almost about 50 ppm FC even though Taylor says 20 ppm. In actual practice it has been reported that it is useful at very high FC levels if you add additional DPD powder. The initial scoop or two will 'flash' pink and then beach out but after an additional scoop or two the pink will "hold" and you can titrate.)

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When it refers to adding "x" oz of a chemical like dry acid... Is that by weight or volume. Usually liquid is volume - you put water in a measuring cup and you can see 1 oz. do you weight the dry acid, like with a scale?

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Dry chemicals are generally by weight. Because of differences in densities of different chemicals 1 oz by weight might not be the same as 1 oz (2 tablespoons) by volume). I use an inexpensive kitchen scale (such as this) for measuring chemicals..

IF the container gives a volume measurement for a certain PPM increase (such as adding 2 teaspoons per 300 gallons or something like that or specifies fluid ounces and not just ounces) then you can follow that but if it just give a measurement for a dry chemical in in ounces, pounds, or grams then it is weight. You can weigh out a known amound of a chemical and you might find that, for example, there are about 4 teaspoons of a certain dry chemical in, say, a half ounce so in the future you could measure THAT chemical by volume. However, be aware that if the manufacturer changes suppliers the volume measurement could change.

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