just because it isn't water soluble doesn't mean that drinking water won't help. There is no way in hell to get rid of all of the fat reserves in your body that have had pot in them at some point, if that would be the case it would take years for pot to get out of your system. think about it, if THC is testable in your piss, which has little to no fat content, it must be getting out of there somehow. There are plenty of other non-polar molecules besides fat in which THC will act like a solute. Not to mention the far less scientific fact that the more water you drink, the more your kidneys or liver (forgot which one gets rid of THC) will be removing from your body.
Anyways, niacin (effectiveness disputed, but it can't hurt), tons of water, lots of exercise, and a whole ton of water and vitamin B12 on the day of your test so your pee stays yellow.
Remember when the signatures were the same shade as the posts, and you used to be able to trick people. And if you are reading this, it is my sig.... Those were the days.