表达 “money down the drain” 的字面意思是 “钱流进下水道”，实际意思是 “花在某件事情上的钱被白白浪费，白花钱”。如果想表示 “把钱打水漂”，则可以说 “throw money down the drain”。
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例句
Trying to heat our house is money down the drain – the heat just escapes through the windows!
我们设法为房子供暖，但就是白花钱，因为热气都从窗户缝里漏出去了！

Buying this second-hand bike was money down the drain – I had to spend so much on getting it repaired!
买这辆二手自行车真是白花钱了，因为我又花了很多钱去修理它！

Building a new car park in the town is money down the drain – there are three other car parks already.
在镇上建一个新的停车场就是在浪费钱，因为已经有三个停车场了。