So yeah, I can't smoke on probation which sucks...but, I've been taking Niacin and drinking tons of water...passed a home drug test for weed... YES!!! So, being 6'0 195 lbs, it came out of my system in about 5 days..sweet, bring on the drug test. Didn't get called in today, but I probably will soon..don't even need that drink now, save it for when I do smoke a lot, then I'll use it to pass..shit man, this drug test stuff is easy to pass if you don't smoke like chimney.
Well it's not just a matter of how much you smoke in one session. It's also a matter of how frequently you smoke. If you smoke only occasionally and don't go crazy when you do smoke then yeah it's not too difficult to conceal things. If however you smoke daily for a long period of time, even if the daily amount is just a little, it will take longer to get clean from your last session.
Another thing to be careful of is the level needed by the test to trigger a positive result. A home test you buy at the store might have a higher cut off point then parole and probation. In other words a home test might come up negative but a test done by parole and probation done at the same time might come up positive. Some tests have a 50 ng/ml cut-off which is fairly easy to pass for an occasional smoker. Other tests however have a 15 ng/ml cut-off and may show up as a positive for as much as 2-3 weeks even for occasional smokers.
Here's a link to a web page on NORML's website that has some useful info about drug testing and marijuana.
http://norml.org/marijuana/drug-testing/item/the-abcs-of-marijuana-and-drug-testing