What would make alkalinity rise naturally??

[doncaruana]

I have noticed that my alkalinity keeps going up, although slowly in general. The only things I've put in the pool this season are bleach, liquid CYA, muriatic acid, and CoverFree and I've not found anything that indicates it would do that (it advertises as pH neutral). I've put enough acid in the pool to bring the TA down about 20 points or more and have even seen it dip, but it's right back up there to 130.

Any thoughts from anyone?

 

[duraleigh]

I see no purpose in the CoverFree, but that's your call.

I would leave the TA alone.

If you feel you need to lower it, do so according to the article in Pool School....not just with acid.

 

[rdhetrick]

Fill water?

 

[pwrstrk]

Is the coverfree one of those liquid solar heating chem's ?


Sent from my iPhone using Tapatalk.

 

[Butterfly]

Did you test the TA of your fill water?

 

[JasonLion]

To elaborate a little on what the others have said, the most likely cause is TA in your fill water. When water evaporates it leaves all of the TA behind. Then when you add water to top off the pool, the fill water brings new TA, which adds to what is already there. Thus, it doesn't take all that high of a fill water TA level to raise the pool TA. Of course this only happens if you get a fair bit of evaporation and add more water to the pool to replace what was lost.

 

[BoDarville]

Is the coverfree one of those liquid solar heating chem's ?

It is marketed as an alternative to a pool cover to help mitigate evaporation. Here's more info on it: http://naturalchemistry.com/Pool_amp_Spa_1/Products/coverfree.html

doncaruana:
I agree with duraleigh that the product is unnecessary. I wouldn't use it and I'm not buying the hype that it takes the place of a cover.

TA is a measure of the water's ability to buffer pH changes. How steady is your pH? If it is fairly steady, I wouldn't fret over the TA. The TA "happy medium" is different for every pool. It may help us if you would post a full set of test results, though.

 

[doncaruana]

Did you test the TA of your fill water?

It's been extremely rainy here this summer so there has been zero fill water. All rain water.

TA is a measure of the water's ability to buffer pH changes. How steady is your pH?

Been rising fairly quickly from 7.2 just a couple of weeks ago to 8 this morning.

FC 4.5
CC 0
pH 8
CYA 60
TA 130
CH 80

I agree with duraleigh that the product is unnecessary. I wouldn't use it and I'm not buying the hype that it takes the place of a cover.

It doesn't take the place of a cover, but it does make a difference. A couple of degrees here and there add up when we get a cold snap. Regardless of its effectiveness, I only mentioned it for completeness, in case someone thought it would affect anything.

If you feel you need to lower it, do so according to the article in Pool School....not just with acid.

From pool school:
The acid/aeration process to lower TA:
Add acid to lower your PH to between 7.0 and 7.2 (this also lowers TA)
Aerate until PH rises to around 7.6 (the only way to raise PH without also raising TA)

That's exactly what I did so I don't understand the "not just with acid" comment, since that's precisely what pool school calls for. Help me understand what I'm missing please...

 

[harleysilo]

The plus aeration part I think was what he meant.

 

[duraleigh]

The plus aeration part I think was what he meant.

Yep.

 

[chem geek]

Rain water can raise the TA if the pH of the rain water is high since it can then hold more carbonates (from carbon dioxide in air). Normally though rain is usually acidic and doesn't contribute a measurable amount to TA.

If you have scale or plaster dissolving (i.e. calcium carbonate being added to the water), then that would raise both the pH and the TA, but your pool is vinyl so that seems unlikely (it's possible to have scale if your calcium is quite high, but again unlikely unless your fill water is high in CH).

 

[JamesW]

liquid CYA

Liquid CYA is Sodium isocyanurate monohydrate, which will raise the TA some. How much have you added?

60 ppm of CYA added by liquid CYA will add [edit]23.25[edit] ppm TA.

Regular cyanuric acid will lower the pH a little, but is TA neutral.

Been rising fairly quickly from 7.2 just a couple of weeks ago to 8 this morning.

I wouldn't consider going from 7.2 to 8 over the course of a couple of weeks to be a particularly fast change. How often do you test? It's important to test often enough to prevent the levels from getting out of range.

Some bleach can have extra hydroxide, which can raise pH and TA a little over time.

 

[doncaruana]

liquid CYA

Liquid CYA is Sodium isocyanurate monohydrate, which will raise the TA some. How much have you added?

60 ppm of CYA added by liquid CYA will add 46.5 ppm TA.

That's great info and I'll consider it the culprit. Thanks!

As an aside, wouldn't it be a good idea then to update the pool calculator with that info, specifically in the "Effects of adding chemicals" section for liquid stabilizer?

 

[JamesW]

I think that I got the calculation wrong. I think that 60 ppm CYA added by liquid CYA should add 23.25ppm TA, not 46.5 ppm.

 

[doncaruana]

I think that I got the calculation wrong. I think that 60 ppm CYA added by liquid CYA should add 23.25ppm TA, not 46.5 ppm.

Regardless of the amount, if it has the effect of raising TA, it seems it should be rolled into the pool calculator...

Can you share the calculation/info you used in the meantime?

 

[duraleigh]

it seems it should be rolled into the pool calculator

The pool calculator is not owned or managed by anyone on this forum.

 

[doncaruana]

it seems it should be rolled into the pool calculator

The pool calculator is not owned or managed by anyone on this forum.

I don't use that one anyway. I meant http://www.troublefreepool.com/calc.html

 

[chem geek]

Adding pure Cyanuric Acid (CYA) does not change the Total Alkalinity (TA) because the lowering of pH and TA of the weak acid (hydrogen ion) counteracts the rise of TA from the salt (cyanurate ion). However, liquid CYA is sodium cyanurate so increases the TA where for every 10 ppm CYA the TA is increased by 3.88 ppm so James' second calculation is correct.

Note that this rise in TA is not due to carbonate alkalinity so is not increasing the rate of carbon dioxide outgassing and is not changing the Calcite Saturation Index (CSI) so is not something someone should worry about or adjust lower if your water chemistry was already in balance and you were just increasing the CYA level.

When you add pure CYA, however, the TA doesn't change upon addition, but the pH is lowered (so carbonate alkalinity is lowered) so depending on how you raise the pH you can affect the CSI. If you let the pH rise from carbon dioxide outgassing, then your CSI will drop relative to where you started, essentially because you've added an acid and aerated (allowed outgassing). In an extreme situation adding 80 ppm pure CYA and having carbon dioxide outgassing bring the pH back to where it was before you added the CYA, the TA doesn't change, but the carbonate alkalinity (at pH 7.5) drops by 24.8 ppm and the CSI drops by 0.16 units. So not a large amount, but not insignificant either.