What device is designed to separate and retain undesirable matter from normal waste?

The device designed specifically to separate and retain undesirable matter from normal waste is the interceptor. Interceptors are commonly used in plumbing systems to capture oils, grease, and other harmful substances before they can enter the municipal sewer system or private treatment facilities. By doing so, they help prevent blockages, protect the environment, and maintain the integrity of wastewater treatment processes. Interceptors are especially important in commercial settings like kitchens and garages where grease and oils are prevalent.

In contrast, a septic tank treats wastewater by separating solids from liquid waste but does not focus on just intercepting undesirable materials like grease. A piping system simply conveys fluids and does not perform any separation function. A retaining basin is generally used for the temporary storage of liquids and does not actively separate waste materials. This distinction clarifies why the interceptor is the appropriate choice for this particular function.