'to go down the drain' definitions:

Definition of 'to go down the drain'

From: GCIDE

drained \drained\ adj. having lost much energy or emotion from vigorous activity; -- of people; as, the day's events left her completely drained of strength. [WordNet 1.5]
2. having resources completely depleted.
Syn: depleted. [WordNet 1.5]
3. having no power remaining; -- of a battery.
Syn: run-down. [WordNet 1.5]
to go down the drain
1. to be consumed in profitless activity; to be wasted; to become worthless.
2. to vanish or cease existing. [PJC]