What you should do first is to pick up a home THC test kit and test yourself so you know for sure where you stand. When testing yourself, be sure to use the first urination of the day when THCA concentrations would be at their highest.

If your home test is positive, and your scheduled U/A is 3 days away, then all exercise should be curtailed until after the U/A is over. When fat cells burn, the stored THC metabolites are released back into the bloodstream, filtered by the kidneys, and are deposited into the bladder fo the eventual exit. Therefore, youd want to be as dormant as possible to prevent a bunch of THC metabolites from being released, which will end up in the urine to be detected.

Drinking water is only helpful on the day of the U/A. Drinking water days or weeks before the U/A is useless. THC is fat soluble and not water soluble. You cannot "flush" THC from the fat cells like you can wash dirt from a car. It does not work that way.

The purpose of drinking fluids is to dilute the THCA concentration that is present in the bladder. The idea is to dilute the concentration to where the urine sample registers below the cutoff thresholds of the drug screen. This dilution phenomena, however, is only temporary - once the fluids ingested had all been urinated out, the bladder is replenished with fresh THCA-laden urine by the kidneys, and thus, the donor would resume testing positive for THC.