Which of the following statements is true regarding plumbing installations subjected to freezing temperatures?

The correct statement regarding plumbing installations that are exposed to freezing temperatures is that they must be protected from freezing by insulation or heat. This is crucial because plumbing systems can suffer significant damage when water inside pipes freezes, leading to pipe bursts and extensive repair costs. Insulation helps to maintain the temperature of the pipes, preventing them from reaching freezing point during cold weather. Alternatively, using heat sources, such as heating cables or maintaining ambient temperatures, can also ensure that water remains above freezing.

The requirement for protection against freezing emphasizes the importance of planning and implementing proper insulation measures and possibly heating methods for any plumbing installations that could be vulnerable to low temperatures. This ensures the longevity and functionality of the plumbing system.

The other statements do not capture the necessary precautions adequately. For instance, simply insulating pipes does not exempt them from needing heat protection in extreme conditions. Locating plumbing below ground might not always be feasible or effective in preventing freezing, and there are indeed specific insulation requirements that must be followed based on local codes and environmental factors; therefore, plumbing installations are not exempt from such requirements.