A couple of little points about the possible flaws in your experiment. You should test with the first void of the day as it is the most concentrated and thus the dirtiest and the wors case scenario. Next, if you were drinking fluids all day long so that you were pissing 20 times, you might have been diluting so your test results don't accurately represent your urine THC metabolite concentration without adulteration. So this means you might not be able to pass the test naturally. There is a difference between being dilute, being clean, and cleaning out your body. You might also be one of the lucky ones who has a short THC elimination half life to begin with.