It naturally leaves between 2-5 days ,,, but drink lots of water as it will dilute the trace in urine
Codeine usually leaves your system in 2-3 days. It is all a waiting game when you need to clear out your system. Any drug test will pick up substances used to try and fool the test and they do not work. Neither does drinking water.
Maybe if you drink a lot, but it also depends on how much you took. But if you are a cornice user I would take some BC powders. I would take about 4 of them and drink a bunch of water and when I say drink water I mean like 2 liters and pee 2 before you get there and if your pee is clear then most likely you are fine.
Drink as much as you can