Just an FYI, I have drained several old cars of stale gas by connecting my spare 12vdc electric fuel pump---I think it was like $12 from Amazon---to the stock line thru a piece of rubber hose and into a bucket. I had no issues with cutting the stock metal fuel lines on those cars to splice in a piece of hose. but I do not know if the DEF lines are high pressure in which case I wouldn't do that. Just a suggestion.
NOTE: Distilled water is $0.80/Gallon at Walmart around here, good enough for my wife's CPAP (she'd let know if otherwise, har!) and my old golf cart batteries.