I have a question about running the Hanna Checker Phosphorus test: How many times do you run the test with the same sample? I ran the test and the 1st result was 17, then I decided to run it a couple more time just to see. I have 2 vials(one with sample and one with tank water) and just kept rerunning the test for a few times. Here are the results 1. 17 2. 7 3. 5 4. 4 5. 7 Which number should I use? Or do a avg of them all?