My Taylor test kit ran out of the reagent to test the CYA levels so I brought a sample of my pool water to the pool store and had them test it. I was only interested in the CYA levels, but they test the FC, TC, CC, PH, hardness, alkalinity, and CYA.
Turns out the CYA was good, but their test showed the PH at 8.1. My Taylor test kit shows it around 7.5. The test they do at the store is one where they use a pipet (I think that's what it is..anyways it picks up a measured amount of water with a plunger you activate with your thumb) and they insert the water into a test tube that's sealed with foil at the top. The test tube then is inserted into a device that I guess measures the color/shade of the water electronically and displays the result on a computer. The test tubes are then recycled (not used again for another test).
It seems that something as elaborate as that should be accurate, but as I said, my test kit shows a much lower PH value. The test kit is about 8 months old. Would a reagent that is a bit old give an inaccurate result, do you think the stores results are the ones I should trust, or are the Taylor tests very accurate?
For comparison I used some cheaper test kits I had lying around, and here's what I got.
Test strips PH7.6
cheap drop test kit #1 PH7.6-7.7
cheap drop test kit #2 PH7.5