What is a common non-visible concern during plumbing inspections?

Corrosion in hidden pipe connections is a common non-visible concern during plumbing inspections because these areas are not easily accessible or observable. Plumbing systems often have pipes that are embedded in walls, floors, or underground, and any deterioration of these connections can lead to significant issues without being immediately detected. Corrosion can result from various factors, such as age, water quality, and environmental conditions, and it can lead to leaks, reduced water pressure, and even complete pipe failure over time. This type of damage may go unnoticed until it causes a visible problem, making it critical for inspectors to be aware of potential corrosion issues in areas that are not readily visible.