Quote Originally Posted by Burnt Toast
Drinking water only serves to dilute the THCA concentration that is present in the bladder. This phenomena is only temporary - once the fluids ingested had all been urinated out, a "dirty" donor would resume testing positive for THC. Therefore drinking fluids is only helpful on the day of the U/A.
I may also add that dilution techniques can backfire if the THCA concentration in the bladder is too high. For most heavy smokers, it would be virtually impossible to dilute that concentration without overdiluting and sending up the red flags at the lab.