plug ‧ hole /ˈplʌɡhəʊl $ -hoʊl/ BrE AmE noun [countable] British English
1 . the hole in a bath or ↑ sink that the water flows out of, and which you can put a plug into SYN drain American English
2 . go down the plughole informal
a) if work or effort goes down the plughole, it is completely wasted:
Two years of hard work went right down the plughole.
b) if a business goes down the plughole, it fails and has to close