Illinois Plumbing Code Practice Exam 2025 – All-in-One Guide for Exam Success!

The correct answer states that duplex pumping equipment is required for sumps receiving the discharge of more than six water closets or 60 DFUs. Under the Illinois Plumbing Code, duplex pumping systems are designed to provide redundancy and reliability for wastewater removal. When a sump system serves a significant number of fixtures, such as more than six water closets or accumulates a total of more than 60 Drainage Fixture Units (DFUs), it indicates a higher demand and potential for increased wastewater flow.

Using duplex pumping equipment ensures that there is a backup pump available in case one fails, thus preventing any possible overflow or backflow that could cause sanitary issues or health hazards. This requirement reflects the code's emphasis on maintaining effective sewage removal systems in scenarios where the risk of failure and subsequent problems is heightened by the volume of waste being pumped.

Other options suggest thresholds that fall below this critical figure, which do not align with the Illinois Plumbing Code's specifications for ensuring system reliability. Hence, the requirement for duplex pumping at 60 DFUs serves to protect public health and the integrity of plumbing systems in high-demand situations.