How long does it take to get one pain pill out of your system?

The time between taking the pills and a clean system depends entirely on the drug in the pills, and specifically two properties: halflife and dosage.

The more you take, the more work has to be done to get rid of it, and the longer it will take to get all the work done; the longer the halflife, the harder it is to get that work done and it will take longer as well.