No, No, and No.

Why?  You will let all of the toilet water and pee run out of the tank(and black tank needs as much water/liquid as possible) and you end up with all of the poop stuck in the black tank, best case you end up with poop pyramid, worst case is it gets all clogged up.

Just don’t do it.

Be sure to check out my youtube channel for video on various topics you see in my blog posts: https://www.youtube.com/channel/UCsppfSs3_Gt1BEJOgeJWbRg/