We use this expression to say that someone has wasted something – normally time, money or effort.
You can use this phrase in ………… language.
A: You bought them quite an expensive present – and now they have cancelled the wedding!
B: I know. That’s £300 down the drain.
A: We all worked so hard preparing for the exam, now they’ve doubled the fee?
B: Yes. That’s a year’s work down the drain, I can’t afford it.