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.
chem geek
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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
chem geek
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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.

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