Alkalinity Question

[Erack]

Hello All!

I have had a pool for 15 years but just a few weeks ago gave my pool store the heave hoe and switched from trichlor tabs to bleach.

I see in the Pool School that the recommended level of TA for a vinyl pool is 70-90+ but to ask the forum for advice on what would be ideal for my pool. It runs east to west on the southern facing side of my house so it gets lots of direct sun. My water test results from this morning are below.

In all the years of the pool store water testing they always had two alkalinity results, a Total Alkalinity result an an adjusted alkalinity result. They always used the adjusted result for making any recommendations. I now have a Taylor K-2006 test kit and it came with a book "Pool & Spa Water Chemistry" that gives a formula and chart to use to get an an adjusted alkalinity result.

When posting TA should I use the results I get from the test or should I use the formula and use the adjusted result?

My pool is crystal clear.

Water Temp - 86f
FC - 4.5ppm
CC - 0ppm
PH - 7.7
TA - 120ppm (109.8ppm is adjusted result using the formula from Taylor)
CH - 80ppm
CYA - 35ppm

Do I need to do anything?

Note: I have not put any Borax in my pool as I have not had to increase PH ( I have some on hand though as well as baking soda)


Thanks in advance!

 

[chem geek]

The Total Alkalinity only needs to be adjusted when calculating a saturation index for calcium carbonate. Our TA recommendations and the calculations in PoolMath automatically account for the recommended or entered CYA and Borates levels that adjust the TA for the Calcite Saturation Index (CSI) calculation. In other words, don't worry about adjusting the TA for calculations.

As for the actual TA level in your pool, the only reason to lower it (since your CH is low since you have a vinyl pool) would be if you find the pH is rising over time too much to your liking. A lower TA will have less carbon dioxide outgassing that causes the pH to rise. Whereas your Trichlor tabs were acidic, the use of bleach is roughly pH neutral but carbon dioxide outgassing from the pool causes the pH to rise. So it's up to you as to whether you want to use the procedure to Lower Total Alkalinity or just want to see how things go. If you add acid over time to maintain the pH, your TA may drop anyway unless you have evaporation and refill with water high enough in TA.

 

[Erack]

Thanks Chem Geek! I'll just stay where I am at and see how things stay.