Correcting only the seat direction gives about 50 percent relief even when the toilet is in a wrong zone. The teacher changed East- and West-facing seats to North-South in many homes with very good results, better than many other treatments, so do this first.
Facing North aligns the body with the magnetic field, and the pressure it puts on the stomach clears the bowels quickly. The rule against facing East or West appears in Vedic texts, the Shiv Puran and Jain texts. A slight tilt, such as facing NNE on a tilted plot, is acceptable.