THC is stored in ur fat cells so water doesnt do shit it might temporarily dilute ur piss enough to pass but if its court ordered they might call you back for inconclusive results. BUT to avoid that after drinkin a shit ton of water. eat a good amount of red meat and eat some b-12 capsules. b12 makes ur piss yellow so it wont look like water and the red meat gives ur piss some enzymes or amino acids or some shittt, I cant remember, that will make the results not look like water.