I having been having a lot of issues of getting concrete test results. I like to match up my test results (TF-100) to a pool stores to make sure my results are valid. So I normally go in weekly to the pool store just to get a water test. I have found that thre results wildly varies between each pool store and my results. I don't know who to trust. For example, yesterday I went to a pool store (Pool Werx) and they told my CYA was at 100, where as my CYA test told me I was at 60. I was shocked as I had drained half of my pool 2 weeks ago and my tests all were in the 55-60 CYA range. I'm in the process of getting back into liquid cholorine instead of tabs (I fell off the TFP bandwagon and trying to get back on). This same thing has happend to me many weeks ago, I went to leslies to get the water tested and they said I was at 100, then i went straight to pool werx who said it was around 60. Any suggestions on how to verify my tests are valid?