Got my TF100 test kit a few months ago. Been using it regularly and use the pool stores to 'sanity check' my results once a month when I go in for chlorine.
7/10/09 - Pool store tests TA at 110 (I'm about the same)
8/03/09 - Pool store tests TA at 80 (I'm about the same)
8/20/09 - Pool store tests TA at 150! (I'm at 70!)
***? My TA has been dropping consistently since I had my pool replastered. Pool store has been generally within 10-20 ppm of my TF100 tests. Now I am testing about 60-70 (It turns red at 6, more red at 7 drops).. so I am thinking I need to add baking soda.. so I go in to have the pool store verify my results and I get this! Sigh.
So I go to a different pool store, and they test it at 140.. I watched the lady do the test, and I counted the drops - It was 14. So now I am completely confused. I don't want to raise my TA if its really in the 140-150 range, but my testing is showing 60-70. Can anyone think of something I may be doing wrong with the test that could cause the results to be off? Its my understanding the 'static' effect on this test would result in my tests being higher than normal, not lower. And I now know how big the drops should be, so I don't think I am doing that part wrong.
Any ideas here? I am filling the container to the 25ml mark. Adding 2 drops of R7, swirling, 5 drops of R8, swirling.. then adding one drop of R9 at a time and swirling until it changes colors.. I get 6 drops until it changes, and 7 when it changes even more. So I guess the result would be 70.