Who is not permitted to design a Class 4 system?

• A. The Inspector
• B. The Owner Of The Property
• C. A Licensed Designer
• D. The Contractor

Answer: (A)

Designing a Class 4 on-site system is handled by a licensed professional because these systems are complex and carry significant public health and environmental risks. The licensed designer or engineer evaluates site conditions, soil performance, pumps and drainage, setbacks, and regulatory requirements to create a safe, compliant plan. The person who designs the system must be credentialed and accountable under regulatory standards.

The inspector, by contrast, verifies that the installed system follows the approved design and code rules. Their role is review and enforcement, not creation of the design itself. That’s why the inspector is not permitted to design a Class 4 system. Owners and contractors aren’t the designated design authority for these high-risk systems; the formal design must come from a licensed designer.