CYA question

I tested my CYA the other day because I went away for a few days and left in a floater with some chlorine pucks.

I just wanted to see how much, if any, my CYA level went up. I used a Taylor 2006c testing kit. Before I left, my CYA was holding at 50. Upon my return, my tests show that it was around 100 now. I didn't think it would have gone up that high, so I had it tested at the pool store. Their test says my CYA is 35. I am not sure why there is such a big difference. I tested it again the next day, and that test showed it to be 60.

Why the big swing???? Is this test more of an estimate than anything? I ask because the level at which I need to hold my chlorine is affected by what the CYA level is.

I would trust your testing over the pool store, any day. The CYA test is very subjective and differences in lghting can have very large differences in your results. That is why it's important toduplicate the conditions during testing as close as possible. That being said, for every 10 ppm of chlorine you got from the trichor, you added 6ppm of CYA. So if you were gone for a couple of days, a 50ppm increase is doubtful. But if you were gone for a few weeks, it could happen....