Which of the following is a common method used for inspecting sewer systems?

Smoke testing is a widely used method for inspecting sewer systems due to its effectiveness in identifying leaks and breaks in underground pipes. This technique involves introducing a non-toxic smoke into the sewer lines. If any smoke escapes through cracks, openings, or faulty connections, it is an indication of a problem in the system. This method is particularly beneficial because it can reveal not only the structural integrity of the pipes but also issues related to infiltration from surface water or storm events, which can lead to significant operational challenges for wastewater management.

In contrast, while UV light testing, magnetic resonance testing, and thermal imaging may have certain applications in various fields, they are not commonly employed for routine inspections of sewer systems. UV light is often used for other purposes such as disinfection processes, while magnetic resonance is more relevant in medical imaging and geological surveys. Thermal imaging can help identify temperature differences but is not specifically designed to assess the integrity of sewer lines. Thus, smoke testing remains the preferred method in this context.