使用後は必ず...

Graffiti on the Wall of a Toilet

The other day, a piece of graffiti on a toilet wall made me laugh. It says:

使用後は必ず水に流してください

LOL

The point here is 水「に」instead of 水「を」. I’m afraid I couldn’t put it into an understandable English to convey the essential point. The punchline「水に流す」(Japanese set phrase) would resist word-for-word translation without the loss of the deliberation of the fun point—that could be a “funny point” instead rather than a “fun point.” Haha.

But consider the following intriguing expression:
これまでのことは水に流して今後はよい関係を築こう。
What has happened up to now is so much water under the bridge. So, let’s go on from here.

ps
水に流す might be:
forget about the past
forgive and forget
let bygones be bygones
wipe the slate clean
wipe it off (slang)
pass the sponge over the offense (archaic)

こちらの投稿もどうぞ：
https://note.com/real_hare9943/n/n341df3402a2e

当方のロゴです↓