By doing a Forum Search with the terms "niacin myth" and "drinking water useless", you'll discover that taking niacin and drinking water days or weeks before a U/A is of no help.

Nobody can realistically answer your question for you. And the so-called "cleanout timetables" should never be relied upon because they are almost always off the mark. Each persons body is different and there are too many variables to take into account. Only testing yourself with a THC test kit (using the first urination of the day for each test) can give you that answer.