My plumber attached my shower area drain and the WC (water closet, i.e. toilet) drain through a single pipe and installed a P-trap at shower drain. The level of the P-trap is such that when we flush the WC some of its water runs into the shower area drain P-trap and it starts emitting a foul smell in the bathroom.
I believe he has installed these drains with a T-joint instead of a Y-joint and level of pipe is not correct as water runs backwards to the shower drain.
Is there any solution to it without damaging the bathroom tiles and floor?