TA test question

[know-nothing]

I have noticed that when I perform the TA test. The color may change for a brief second from Green to pink but it takes another 2 drops before the change becomes permanent. So I record the amount to make the change permanent. I am doing the right thing?
I ask because I went for a water check at the local Leslie's pool. They told me that my TA is 50. When I repeat the same test with my kit, I do see this brief color change at 50 as described above but the color change only becomes permanent at 70.
Who is right?

Thanks

 

[Guest]

Leslies is doing it wrong... no surprise here. Continue to titrate until one more drop does not produce any further color change and then do not count that last drop.

 

[numberonenole]

That is the same thing I was wondering! Is it the same for all tests? Thanks!

 

[JasonLion]

Yes, all of the titration tests (add one drop at a time till the color changes) work that way.

 

[Guest]

All the common ones used in pools. The salt titration test and the borate titration test are slightly different and a bit moe complicated since have endpoints at the first stable color change and can be overtitrated easily. This is one of the main reasons that we recommend strips for these two tests (and because the strips give results that are quite precise for the salt and within the precision needed for the borates.)