Interpreting TA color change question

[Traveller]

I have been testing my water myself for the first time this year thanks to this forum, but I still get my water checked periodically at the local pool store if I am going near it.

My test results and theirs seem to be fairly close except TA where they always show me lower than I show. For example yesterday I show TA=170 and they show TA=129. Prior tests have been about the same with the pool store about 40 less than my result. These are all done around the same time and with the same water sample.

So my question is if I am reading the test wrong. For example, the above test of 170 was green until about the 15th drop when it turns kind of green/purple, then on the 16th drop it may be more of a very dark purple, then on the 17th it goes more of a red / pink. So I am calling that 170.

Is the correct method to count until red, or count until not green?

Thanks!

 

[JasonLion]

Always trust your results over the Pool Store's results. You are doing the test correctly and their results are almost certainly wrong.

Technically, you add drops until the color starts changing and then continue adding drops as long as the color continues changing. The final drop, which does not change the color any further, does not count.

 

[Traveller]

Awesome - thank you for the clarification.

 

[duraleigh]

but I still get my water checked periodically at the local pool store if I am going near it.

Trust your own testing! You will never be a complete BBB'r until you learn that your testing is almost always more accurate than the pool store. Double checking yourself against a poor resource only leaves you with doubt.

Now, the color change tests (TA, CH, FAS/DPD) all look for the same thing....a complete transition of color, no matter what the beginning or end color is. So, when you do the TA test, you continue to add and count dreops until the last drop produces no color change whatsoever...none...nada...zilch. :lol:

Once that occurs, you subtract that last drop (that made no change whatsoever) from your drop count and that is your test result.

i.e.

10th drop...big change

11th drop....some change

12th drop......very little change

13th drop......no change whatsoever

TA = 120

(JasonLion already posted so this is just in case you needed emphasis!)

 

[Traveller]

Exactly what I was looking for. Thanks guys.

... And I got the other lesson as well - "Trust in thyself is the second law of BBB" (the first law being "Get thyself a tricked out test kit young aqua-head").

 

[duraleigh]

(the first law being "Get thyself a tricked out test kit young aqua-head").