Nobody can realistically and accurately answer your question as to if you have a chance to legitimately pass a U/A. Each persons body is different and there are too many variables to take into consideration to arrive at a guesstimation. Only periodic testing with a home THC test kit (using the first urination of the day for each time) can give you that answer.

Drinking water is only helpful on the day of the U/A. Drinking water in the days before the U/A is of no help. To find out why, read post #4 in this thread: http://boards.cannabis.com/drug-test...-approved.html

Exercise is helpful is you have weeks to prepare. However, if your home test is positive and the scheduled U/A is 3 days or less away, then all exercise should be curtailed and the person should be as dormant as possible to avoid releasing a bunch of THCA into the bloodstream, which will end up in the urine to be detected.

Under the criteria set by US Dept of Health & Human Services, a "non-human" sample is determined if the creatinine level is less than 2 mg/dL and the specific gravity is less than 1.001 or greater than 1.020. As long as the synthetic batch is unexpired and had not been exposed to direct sunlight, it will pass these checks.
Drug adulteration test kits can be purchased dirt cheap online (by doing a google search), to check that the synthetic batch will fall within acceptable ranges. These test kits are also helpful during the utilization of dilution techniques.