They 'flushed' impurities from the system. = They 'flushed' impurities out of the system.
She published her first novel while still 'in the flush of' youth. [=while still young]
The committee succeeded in 'flushing out' [='finding'] several good candidates.
(..) I'd like to report a problem with one of your mechanics. When did you bring your car in? Yeah, right. I'm gonna get my car repaired at a dealership. Why don't I just flush my money down the toilet? Sir, what exactly is the problem? One of your guys, Kip or Ned-- Short name. (..)1998 TvShow: Seinfeld Title: The Dealership Season: 9 Episode 11