Why the big discrepancy in Total Alkalinity?

[mgianzero]

I brought my pool water to local store to measure the salt level because my salt cell was saying it was low. Indeed my salt was on the low end - so I'll add more salt. Simple.

But then she told me my total alkalinity was 21. TWENTY-ONE! I've never heard of pool water reading that low. I went home and re-tested mine (previously it was 60) and it came back at 70 using the TFT pool kit. How can they be so far off? She couldn't tell me the name of test - just that "it's run in the computer" whatever that means.

I came back 2 days later for another bag of salt. This time she tells me my total alkalinity was 18. What? I had my son (a completely different person who's never done the test before) test my water again. He also measured it at 70. Who do I believe?

 

[PoolStored]

I am Pool Stored. Stay out of the Pool Store. Ask me how I know.

Seriously, just trust your test kit and avoid the pool store (at least the testing and advice...where you buy recommended chemicals is up to you).

 

[ajw22]

Who do I believe?

Believe your lying eyes and your TF-100 test kit.

 

[generessler]

If you poke around the pool school info and many, many questions similar to yours, you'll see it stated just as many times that you can't trues pool store tests. Machine calibration. Tech training. Dishonest attempts to sell you chemicals. They're all there. TA test is one of the easiest to do perfectly. Unless your reagents are damaged (old, frozen, etc.), you're getting an accurate answer.

 

[JamesW]

Adjusted TA = TA – (CYA X CYA C.F) – (Borate x Borate CF)

Borate C.F (correction factor) based on pH.

pH.......CF

7.2.....0.051

7.4.......0.0786

7.6......0.1248

7.8......0.1989

Cyanuric Acid correction factor based on pH.

pH........CF

7.0.......0.22

7.1.......0.24

7.2.......0.26

7.3.......0.28

7.4.......0.30

7.5.......0.32

7.6.......0.33

7.7.......0.34

7.8.......0.35

7.9.......0.36

For example, if the pH = 7.6, TA = 90, Borate = 50 and CYA = 70, the adjusted alkalinity is 90 - (70 x 0.33) – (50 x 0.1248) = 60.66.

 

[an1vrsy]

Why the big discrepancy in Total Alkalinity?​

The pool store wanted to sell you something to compensate for the supposed low TA. Did you buy the product they recommended?

 

[Jimrahbe]

m,

Get yourself a Taylor K-1766 salt test kit and stay the heck out of pool stores...

Really, one of the tests that they screw up the most is the salt level.

Thanks,

Jim R.

 

[Mdragger88]

Adjusted TA = TA – (CYA X CYA C.F) – (Borate x Borate CF)

Borate C.F (correction factor) based on pH.

pH.......CF

7.2.....0.051

7.4.......0.0786

7.6......0.1248

7.8......0.1989

Cyanuric Acid correction factor based on pH.

pH........CF

7.0.......0.22

7.1.......0.24

7.2.......0.26

7.3.......0.28

7.4.......0.30

7.5.......0.32

7.6.......0.33

7.7.......0.34

7.8.......0.35

7.9.......0.36

For example, if the pH = 7.6, TA = 90, Borate = 50 and CYA = 70, the adjusted alkalinity is 90 - (70 x 0.33) – (50 x 0.1248) = 60.66.

This
They use this adjusted TA to calculate lsi/ csi (whichever they use)
but PoolMath does all those calculations for you so there’s no need to adjust your ta calculation based on cya so you can just input your actual TA.
Generally pool stores often also recommend a higher TA range than tfp because of their recommendations to also use acidic chlorine products like pucks & powdered “shock” which will tank your ph & subsequently TA in short order.
They also like to sell really expensive soda ash & baking soda. It’s their bread & butter.
As mentioned several times already - Your TA is fine, don’t sweat it, trust your results
Also, get yourself a k1766 so they never need to test your water again

 

[mgtfp]

They want to get you fixed on the white powder they are selling for outrageous prices.

You shouldn't trust anyone trying to sell white powders as treatments for non-existent problems. Eventually, you'd end up with real problems created by the white powders themselves.