Reduce Total Alkalinity Levels

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
PTSNevada

Reduce Total Alkalinity Levels

Postby PTSNevada » Sun 23 Aug, 2009 12:26

I use a Taylor K-2005 test kit and it includes a 'Watergram' wheel that helps establish water balance. This is a slide rule type device which calculates LSI (Langelier Saturation Index; Google it). In a nutshell - Calcium, Total Alkalinity, pH, and Temperature are like four legs of a chair and this chair wobbles and can almost never be made to sit perfectly level on the ground, particularly in a volume of water that is open to the elements. One factor that is rarely in this calculation is Total Dissolved Solids (TDS) which based on your story, I assume it is probably way high. If it is over 2000ppm then you are due for a complete or partial drain and refill. If you are using well water and its balance is off, it may be adding to the problem. I suggest you take samples of your pool water and tap water and send it off for a full water quality test. TDS is a pain to measure accurately but cheap electronic meters are available for $20 or so that will get you a ballpark measurement. The other ballbark measurement is the taste of the water - if its salty or minerally sweet then its worth checking.

The other thing is that Cyanuric Acid makes the TA measurement inaccurate. The simple rule is Actual TA = TA - (CyA/3). This varies by pH as well but the last page of my Taylor kit manual says if your pH is 7.2 then the formula is Actual TA = TA - (CyA*0.26) and if the pH is at 7.5 (your target) then the 1/3 is correct. If CyA is over 150ppm then you need a drain and refill. (Some local health departments limit it to 100ppm, and there are some claims that CyA may be a carcinogen)

CyA (Cyanuric Acid) is part of the Trichlor molecule and has the effect of preventing sunlight from destroying Chlorine but if CyA is over 40ppm, it is not any more effective at doing so. Therefore to me, it makes sense to use Trichlor until you get to 40ppm and then switch to some other method, like bleach or higher concentrated Sodium Hypochlorite from the pool store. Even better, and since you have algae growth, is to pay someone to come in with Chlorine gas tanks and superchlorinate it to 30ppm. It will make the pool unusable for a day or more and you'll probably want to make a day trip somewhere with all the kids and pets and warn all the neighbors while the pros do their thing. This will also blow away all the Chloramines (Combined Chlorine) which may be another part of your problem.

You don't mention your Calcium reading but you do say you have white stuff on the edge meaning its scaling. If your water is too high in Calcium then the only way to get rid of it is to drain and refill, either partially or completely. This can be exasperated if your system includes an autofiller and you have a lot of evaporation and also if your tap/well water is high in calcium to begin with (hard water).

Most instructions pool owners receive to simply keep all of these measurements within a certain range and typically this will result in the near balanced water. If you have excel or other spreadsheet, you can do alot better. Here is a formula that calculates LSI which tells you your water balance (scale formation/dissolution potential):
=9.3+(0.1*(LOG10(B1)-1))+(-13.12*LOG10((B2+459.67)*5/9 )+34.55)-((LOG10(B3)-0.4)+LOG10(B4))
B1 = TDS (Assume 200ppm if its unknown)
B2 = Water Temperature in Farenheit ((B2+459.67)*5/9 converts F to Kelvin)
B3 = Calcium Hardness
B4 = TA corrected for CyA

The resulting number is the pH of Saturation and if you subtract the measure pH from this number then the result is the LSI. The LSI needs to be within +/- 0.5 of Zero. Large Positive Values mean that white stuff on the edge of the pool, Large Negative values mean the water will dissolve the white stuff and possibly concrete and metalwork along with it. http://www.corrosion-doctors.org/Cooling-Water-Towers/Index-Langelier.htm

The nice thing about having it in a spreadsheet is you can play with the factors you can easily control - TA, Calcium Hardness, and pH and get it to a near Zero LSI. Once that is in control, sanitation concerns are much more easily dealt with.


chem geek
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Reduce Total Alkalinity Levels

Postby chem geek » Sun 23 Aug, 2009 16:49

The Pool Calculator will calculate the saturation index and will adjust the TA for CYA automatically and also account for TDS. This calculator essentially matches the Taylor Watergram at low TDS (non saltwater pools) and is more accurate than traditional formulas which are out-of-date.
barbados1

Reduce Total Alkalinity Levels

Postby barbados1 » Wed 02 Sep, 2009 20:41

I'm back!

Bought the TF100 test kit (it is GREAT!)
Bought a magnetic mixer
Bought a electronic pH meter
Read much of the pool school but I'm getting confused with so much information

Here's what I have now:

pH=6.9 (electronic pH meter)
TA=90
CYA=120
Calcium Hardness=340
Chlorine=2

Am unable to raise the pH even with large doses of pH UP
Still have white staining on the black gunite.
two 3" tablets of chlorine are gone in 24 hours. :shock:

What's the best way to lower the CYA? And is that looking like the only problem that you see?

Thanks for your help

-dave-
Medford, Oregon

------------------------------------
15,500 gal in ground gunite pool apx 27 years old
new sand filter with 1HP pump
I run the pump daily for six hours and backwash/brush add aglecyde once a week.
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Reduce Total Alkalinity Levels

Postby chem geek » Wed 02 Sep, 2009 22:32

Double check the pH with the TF100 kit, just to make sure.

As for the CYA, it can only be reduced through dilution of the water and then avoiding use of stabilized chlorine (i.e. Trichlor and Dichlor). The dilution should also reduce your high CH unless your fill water is high in CH.

Don't use any more pH Up since your TA is already reasonable and with the high CH you don't want to get scaling. If you switch to using hypochlorite sources of chlorine, then try aerating the water to see if that raises the pH or try using 20 Mule Team Borax. It doesn't make any sense at all that pH Up wouldn't raise the pH at all -- you can try some experiments in a bucket of pool water to see if you get pH movement (using very small amounts of product).
Guest

Reduce Total Alkalinity Levels

Postby Guest » Wed 02 Sep, 2009 23:20

Thank you Mr. Geek!

I'll do some tests in a bucket with the pH UP to see, but 2# don't move the Ph up on the cube (much).

It looks like the dilution is the key, then aeration and a switch to bleach. I'll give the borax a shot, too.

I'll let you know how it's going and thanks so much for the help!

-dave-
Medford, Oregon
ming

Reduce Total Alkalinity Levels

Postby ming » Mon 14 Sep, 2009 12:26

Hi, all!

Just wanted to report back with my accomplishments.

Did three drain-fills from one foot below the skimmer, apx 3/4 of the 15,500 gallon pool.

Here are the readings from the TF-100 test kit:

pH = 7.32 (slowing raising with Borax)
TA = 70
CYA = 80 (!!!!!)
CH = 150
Fc = 1.5
CC = 1.0
TC = 2.5

The visable part of the outcome is that I now have chlorine available. The above reading is AFTER 4,000 gallons of water replacement prior to which I added 1 gallon of bleach! When the CYA was 150, chlorine couldn't be found six hours after application. GRIN!

I'm using the TRICHOR tabs for doorstops now, liquid bleach is always on my shopping list. I assume without the trichor, CYA will fall a little more without water replacement. When it gets down to 50 is that the time to throw in a trichor tab or two to elevate the CYA?

What does a person do now for shocking for winter? We used to use non-chlorine shock in November, should I continue with that practice or just bleach-it big-time?

Thanks so much, Richard for your help. I was totally lost and now I'm beginning to understand the process, something I should have been following for years.

Everytime I do a pool test and find it is good, I'll remember your kindness and help.

Thanks! :mrgreen:

-dave-
Medford, Oregon
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Reduce Total Alkalinity Levels

Postby chem geek » Mon 14 Sep, 2009 21:41

Dave,

Thanks for the compliment and glad things are working better for you. With a CYA of 80 ppm, you'll want to maintain a minimum FC of 6 ppm to prevent algae growth unless you spend more money using a supplemental algaecide such as PolyQuat 60 or a phosphate remover. Read the Pool School to learn more about how to maintain your pool, including the proper FC for each CYA level.

Yes, the CYA should drop over time as the water slowly gets diluted from splash-out and from backwashing if you have a filter that gets regularly backwashed (such as a sand filter).

As for when to start using stabilized chlorine to raise the CYA again, it depends on your situation. With a pool cover, the CYA can be a lot lower -- as low as 30 ppm. If your pool gets a lot of direct sunlight in southern latitudes such as Florida, Texas, Arizona, etc., then even 80 ppm might be better at helping to hold more chlorine (even with the higher FC target). You'll just have to see how things go in terms of daily chlorine usage. If you only lose 2 ppm FC per day or less, you are in pretty good shape. With a pool cover, you can get to 1 ppm FC or less per day. Without enough CYA and in very hot sunny areas, you could lose 3 ppm FC per day (or even more if the CYA is very low).

As for winter preparation, it depends if you lower your water level and turn off your pump because of freezing climate. In that case, wait as long as you can until the water gets very cold (below 60F and preferably below 50F) and then shock with chlorine and add a large dose of PolyQuat 60 with the pump running for a day and then do the closing procedure. In the spring, open up as soon as the water has started to warm up even a little, but not more than 50-60F, and add chlorine.

If you live in a climate where you don't need such winter shutdown procedures because the climate doesn't freeze long enough to be a problem, then just maintain chlorine levels through the winter. The cooler water will consume far less chlorine, especially with a pool cover. Probably less than 1 ppm FC loss per 1-2 weeks, if that.

Richard
atlantispoolchemicals

Reduce Total Alkalinity Levels

Postby atlantispoolchemicals » Fri 18 Sep, 2009 17:50

Atlantis Pool Chemicals PH Decrease does the job exeptionally well. PH down: Lower your PH with our PH minus. It contains 100% sodium Bisulphate.Your pH should be kept between 7.2 and 7.6 range. Granular Acid (Sodium Bisulphate) to lower the pH of pool and spa water.
poolspachemicals uk
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Reduce Total Alkalinity Levels

Postby chem geek » Sat 19 Sep, 2009 02:10

Dry acid (sodium bisulfate) adds sulfates to the water which at higher levels can cause various problems including degradation of stone from magnesium sulfate splash-out and can interfere with the proper operation of saltwater chlorine generator (SWG) systems. Muriatic Acid (31.45% Hydrochloric Acid) will only increase chloride levels and one can get half-strength which fumes less. Do you tell your customers that?
Paris

Reduce Total Alkalinity Levels

Postby Paris » Tue 25 May, 2010 13:12

Reading all the post i am thinking, shall i go to salt water chlorination?
Will i still have the CY acid, hardness and alkaliniy problems?

I have hight CYA, Alk and low hardness and all the post makes me waste a lot of my time with the pool. the pool was supposed to be fun.
chem geek
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Reduce Total Alkalinity Levels

Postby chem geek » Wed 26 May, 2010 00:16

The only way to lower the CYA level is through water dilution, including partial drain/refill. To prevent the CYA from rising, you can use 6% unscented bleach or 10% or 12.5% chlorinating liquid. If your CH is low, you can also use Cal-Hypo at least for a time. When using these sources of chlorine you have to add the pool every day or two unless you have a pool cover in which case you can usually add the chlorine twice a week. This is what I do in my own 16,000 gallon pool shown here and here and it costs only $15 per month including the small amount of acid I add every month or two. I don't need to use any algaecides, phosphate removers, metal ions, clarifiers, flocculants, or weekly shocking. The same is true for most of the tens of thousdands of pool owners on multiple pool forums including this one, The Pool Forum and Trouble Free Pool.

You can also get automated dosing systems (The Liquidator or a peristaltic pump) but if you don't want to buy chlorine regularly then a saltwater chlorine generator (SWG) will generate chlorine on-site from the salt in the pool. With most SWG pools, the main issues are rising pH and adding a lot of acid to compensate, but these things can be mitigated as described in Water Balance for SWGs. If you have soft stone coping or hardscape, then you should seal it since salt splash-out can damage soft stone.
Guest

Reduce Total Alkalinity Levels

Postby Guest » Fri 04 Jun, 2010 09:50

Larry one quick question my total alk is slightly elevated you said aeration would help reduce so I have pointed my return up so it actually shoots out and creates a splashish bubbly area would this be adequate to create the necessary aeration
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Reduce Total Alkalinity Levels

Postby chem geek » Fri 04 Jun, 2010 21:28

It isn't aeration that reduces TA, but the addition of acid that reduces TA. The aeration is so that you can raise the pH without changing the TA so that you can add more acid. If you only added acid to lower the TA, then the pH would get too low. It is the combination of acid addition with aeration that results in TA getting lower without lowering the pH overall.

Yes, your aeration from returns pointed upwards can work well and is what I've done in the past in my own pool, turning the pump on high as well (if you have a variable speed pump).
Billjohn

Reduce Total Alkalinity Levels

Postby Billjohn » Mon 05 Jul, 2010 13:36

Larry,
For thirty years I have had a 20,000 gallon indoor pool filled with well water. During that time I have tried diligently to lower the 230 ppm TA to the recomended 130 for painted pools. The chemical people have always given me the same "voo-doo" advice that you refer to as the slug method. Even though it never worked, I just kept doing the same thing expecting a different outcome because they all said the same thing. Finally I just gave up and accepted the scaling. Recently, I decided to install a geo-thermal pool heater but knew that it would not tolerate the scaling. I came across your post concerning the use of aeration and acid. I had an old 1/2 hp shallow well pump which I rigged with a hose nozzel and dip tube to suck water from the pool and blast it back into the surface at the location of a return. With a little experimentation I found that I could run the aerator constantly, add 2 quarts of acid every 2 hours, and drop the TA 10 ppm every 2 hours with the PH always testing at 7.2 at the end of each 2 hour period.
You would not make a very good chemical salesman, but I can't tell you how much I appreciate your sharing this information with me.
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Reduce Total Alkalinity Levels

Postby chem geek » Mon 05 Jul, 2010 15:02

Isn't it ironic how the "chemical people" don't really understand chemistry? The principles are basic first-year college chemistry yet the pool/spa industry is driven a lot by hearsay and baloney, some of it to drive more profits while some of it is just someone making a mistake and everyone else repeating it like lemmings.

Ben Powell at The PoolForum in this post described the acid/aeration procedure while the slug or acid column method was discredited in this JSPSI report. Note that it isn't that the slug method doesn't work -- the amount that the TA drops is solely a function of the amount of acid added and not how it is added -- it's that it can be dangerous and can result in a very low pH (if you try raising the pH with a base, then the TA rises as well defeating the purpose of adding the acid). Adding 25-1/2 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 10,000 gallons lowers the Total Alkalinity (TA) by 10 ppm and it doesn't matter how you add that acid in terms of that lowering of TA (obviously it matters in terms of safety to pool surfaces so the acid should be added slowly over a return flow in the deep end with the pump running). The trick is how to lower the TA substantially without lowering the pH too much since that can harm pool surfaces and equipment. The answer is to add the acid in steps and aerate the water since that raises the pH with no change in TA -- it forces carbon dioxide out of the pool. Pools are intentionally over-carbonated in order to provide a pH buffer and to saturate the water with calcium carbonate to protect plaster surfaces.

As for the ideal aeration, have the bubbles be as small as possible and put the pipe outlet in the deep end so the bubbles have maximum time exposure in the pool. A pipe or tube with very small holes would work well. It sounds like you've got a great system since 10 ppm TA drop per hour is very good. Disturbing the water surface also works well. You want to maximize the surface area between the water and air any way you can.

By the way, 130 ppm TA for painted pools is also a bunch of bunk. There is no single absolute TA number that is the "right" number. What is required for plaster pools is that the saturation index be near zero and that is a combination of pH, TA, CYA, CH and Temperature. You can calculate the index using The Pool Calculator. If you find that your pH tends to rise too much over time, then the TA level is probably too high. When using hypochlorite sources of chlorine, one should usually have the TA be at 80 ppm or lower. The TA should only be higher if you are using acidic sources of chlorine such as Trichlor (or even Dichlor since it is net acidic when accounting for chlorine consumption/usage which is an acidic process). You need to watch your Cyanuric Acid (CYA) level when using stabilized chlorine sources. Read the Pool School for more info.

Richard

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