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.
(..) Cold mush shit. I love cold mush. "What do you like to do when you're not hiking, Cheryl?" I like to sit on a real toilet. And flush. I like to cook food. Eat food with other people. People, that's another thing I like. I like talking to people, listening to people. (..)2014 Wild