Funny English on signs isn’t all that uncommon here, but it is now not very common to find incomprehensible English. Usually it’s just funny grammar or a funny word choice . . . but my mom gets props for finding this rarity in the restroom at the Confucian temple here in Tainan.
Essentially the sign is a reminder to flush.
Lawrance says the second phrase is a poem and has a double meaning. Literally it is something like “spring mud clearly leaves no mark/trace.” So, it’s kinda supposed to be a play on words about making sure you leave nothing behind in the toilet.