Final answer:
The clearance around a water closet should be at least 30 inches from the side wall and 18 inches from the rear wall as required by the International Residential Code and the ADA.
Step-by-step explanation:
The student's question is about the required clearance around a water closet as per building and plumbing codes. According to the International Residential Code (IRC) and the Americans with Disabilities Act (ADA), the minimum clearance around a water closet should be 30 inches (762 mm) minimum measured perpendicular from the side wall and 18 inches (457 mm) minimum measured perpendicular from the rear wall. This clearance ensures that fixtures are accessible and provide ease of use, and it also allows adequate space for cleaning and maintenance.