Is it important to test immediately after taking water sample or can test be done 30 min or so after getting sample. For example, pool sample brought into house and did a FAS-DPD test and came up with number. Thought I would repeat but it was maybe 30 minutes later and it resulted in a lower number. I usually test immediately but wasn't able to do so this morning. I was trying to do the OCLT and the first test indicated no loss, then subsequent test, I had lost 1.