Dilution reduces the THCA concentration present in the bladder to where the urine sample can register below the cutoff thresholds of the drug screen (that is providing that the THCA concentration is not too high). However, the dilution phenomena is only temporary - once the fluids ingested had all been urinated out, the bladder is replenished with fresh THCA-laden urine, and thus the donor is right back to square one.