How are underground piping systems tested according to NFPA 13?

The correct response emphasizes the importance of hydrostatically testing underground piping systems to ensure their integrity before they are buried. This testing method is critical because it allows for the identification of any potential leaks or defects that could compromise the system's performance in the event of a fire. Under NFPA 13 guidelines, the hydrostatic test involves filling the pipes with water and pressurizing them to a predetermined level, holding that pressure for a given duration to detect any loss, which would indicate a flaw in the system.

This rigorous testing is essential in maintaining safety standards and ensuring that the underground piping can effectively transport water to the sprinkler system when needed. In addition, it combats potential issues of corrosion or structural weaknesses that might not be visible once the pipes are buried.

The other options do not align with NFPA 13 requirements. For instance, simply installing the piping does not exempt it from testing, regardless of the installer’s qualifications. Visual inspections alone are not sufficient to verify the integrity of a buried system, as they cannot detect all possible weaknesses or leaks. Lastly, testing only with air pressure is not adequate; water is used for hydrostatic testing because it is more effective at identifying leaks due to its incompressible nature. Overall, option A is