That would be a BAD BOY yell for me, I wouldn't want to have to clean that everyday.

I would try to put a little food in there, and maybe spray the tub with some urine remover for now. He's gotta break that habit, you may have to keep the bathroom door closed, it sounds funny though. My friends yorkie is 3mos old and pees when she picks him up. But now the
1st sign of his wiggle, she runs him to the pad, or puts him outside so he will know to pee.