07:48 Nov 19, 2009 

A similar question came up just the other day, albeit in a different context.

It's important to note that flushing doesn't just mean 'emptying' — it usually implies the use of one fluid (e.g. sometimes water, or a relatively inert gas like nitrogen) in order to 'push out' the fluid previously in the pipe, tank, system, etc.

So IMHO, the answers already suggested only tell half the story, and I firmly believe that a proper technical term surely must exist in FR?

I have come across 'balayer', which has a similar meaning in this kind of context, though really translates 'scrubbing'. I'd recommend you to keep on looking!