Vicodin and drug tests

[sometimesx345]

A week ago my parents found my stash and on Monday they're giving me a drug test. They know I'll test positive for THC, that's not what they're worried about, they're looking to see if I took anything else as well. Today I got my hands on 20mg of vicodin, and I'm really looking forward to taking it. I know the best option is to wait for after the drug test, which is what I'll probably end up doing, but if possible I'd like to take it today. I'm small (125 pounds), with a relatively high metabolism. I know hydrocodone is not normally tested for, but my parents are specifically looking to test me for everything they can, and for that reason I'm suspicious that they might test me for it. I also, of course, don't want a false positive for morphine or any related substances. If I took it today I would be tested in a little less than 72 hours, is this enough time to be clean? Is there anything I can do to be SURE that I'll be clean? I knew someone who regularly used cocaine and would drink a gallon of water before her test and passed. Would drinking a lot of water over the weekend ensure me to test positive?