In what locations should aluminum alloy pipe not be used?

Aluminum alloy pipe should not be used in exterior locations or underground due to its susceptibility to corrosion. While aluminum itself has some natural resistance to corrosion, when subjected to prolonged exposure to moisture, soil, or various environmental contaminants found in these locations, the integrity of the pipe can be compromised. This is particularly relevant in underground conditions where moisture can be present continuously and may contain salts or other corrosive elements.

In contrast, other conditions mentioned in the choices may have varying levels of tolerance or protective measures that can mitigate risks associated with aluminum. For instance, wet locations or areas with high humidity (as mentioned in one of the choices) may offer some consideration for protective coatings, but leaving aluminum exposed in outdoor or underground environments is particularly risky due to continuous exposure to conditions that lead to more severe deterioration.