As a less confrontational reply: from my point of view “unwanted fly tipping” is talking about rubbish. The concept of depositing unwanted, yet usable, not rubbish, things somewhere is not something that would happen (outside of the rather recent disposable culture context).
As to your sentence (which is perfectly fine), the use of words avoids possibly confusing repetition. Atypical use would be preferred to “no fly tipping, take it to the tip”.
