Illinois Plumbing Code Practice

The correct answer is supported by the Illinois Plumbing Code, which stipulates that unions must be installed within 5 feet of regulating equipment, water heaters, water conditioning tanks, water conditioning equipment, pumps, and similar devices. This requirement ensures that maintenance or replacement of these critical components can be performed efficiently and without undue strain on the plumbing system.

Additionally, the code specifies that for smaller equipment that can be unscrewed, only one union is needed. This guideline reflects a practical approach to installation and maintenance, facilitating easier access while minimizing the number of unions required for simpler systems.

The other options do not align with the specified distances and requirements outlined in the code regarding the placement of unions.