I wanted to check my FC overnight before the pool came on in the morning at 6:30 am. I was up with the baby at 3 am so decided to pull a sample then, in case I didn't feel like getting up at 6:30. When I tested the sample sometime around 7:30 or so, the FC was less than it had been last night. I figured I need to SLAM and went out to get some bleach at Walmart, but now I thought I should confirm that the sample, just by leaving it to sit those few hours, wouldn't have lost FC on its own. I was using a large syringe to draw the water and that's where the water was kept.