Which of the following can be a sign of a potential leak in a plumbing system?

Unexplained water stains are a clear indication of a potential leak in a plumbing system. These stains may appear on walls, ceilings, or floors, and signal the presence of water where it shouldn't be, which is often caused by leaks in pipes or plumbing fixtures. Detecting these stains early is crucial, as they can lead to more significant water damage, mold growth, and structural issues if left unaddressed.

In contrast, high water pressure might not directly indicate a leak but rather suggests a potential problem with the plumbing system that may cause future leaks. Clear water in pipes is a normal observation and does not signal issues, while dry fittings indicate that there are no visible leaks in those areas. Thus, identifying unexplained water stains is a critical step in plumbing inspections to prevent further damage.