If you're not a regular smoker, it gets out of your system relatively quickly. If your'e taking a drug test ~1.5 weeks after smoking it for the 10th time in your life, assuming the other 9 times weren't also all recent, you can take the test with no worries and pass it. For regular smokers, there're herbal cleansers available in smokeshops and through online order. They taste godawful and won't get it out of your system completely - but they will cleanse you of it for the few-hour period in which you take your test. I've passed tests using these when I was a daily smoker. The water method will only work if they're not specifically looking for it. It's a free, widely known way of passing tests and so some of the more thorough places will look for it. It won't make you fail if they know you're doing it, but it won't make you pass either. The cleansers I mentioned will fortify the urine so that this isn't apparent.