A water heater shall have a level working space not less than ____ inches in length and ____ inches in width in front of the control side.

The required working space in front of a water heater is established to ensure safe and effective access for maintenance and servicing. The correct standard specifies that a water heater must have a level working space not less than 30 inches in length and 30 inches in width in front of the control side. This dimension is considered adequate to provide the necessary room for technicians to operate the controls, perform inspections, or carry out repairs safely without any obstructions.

Choosing 30 inches aligns with safety practices by allowing enough space not only to access the controls comfortably but also to avoid potential hazards that might arise from inadequate working space. The other dimensions listed, such as 24, 36, and 48 inches, either do not meet the minimum requirement or exceed it, which, while potentially offering more space, is not the standard specified by the International Plumbing Code for basic functional access adjacent to the control side of the water heater.