Drug Question

Ok .. First off, I'm getting a drug test in the near future (about a week) for a job I'm applying for. It's a simple urine test, nothing too in depth. I'm around 130 pounds, maybe less, with a very high metabolism .. I can eat all day, and not gain a pound. I smoked one week ago, and two days before then, and before that, was an every day smoker. I've been drinking 12 or more tall glasses of water a day, combined with niasin and a shot if vinager .. And I use the bathroom like crazy. How long do you think it will be before the pot is out of my system? I'm taking the test regardless, as I really need this job, and I'm fairly sure I'll be able to pass it, as I drink water almost constantly ... But .. I need someone elses opinion. Thanks. :)