A residential building in a cold climate is experiencing frequent plumbing leaks in its hot water recirculation lines, which are constructed from PP-R pipe. Upon inspection, the plumber notes several areas where the pipe has sagged and appears to be under stress. What is the most likely cause of these failures?

Question: A residential building in a cold climate is experiencing frequent plumbing leaks in its hot water recirculation lines, which are constructed from PP-R pipe. Upon inspection, the plumber notes several areas where the pipe has sagged and appears to be under stress. What is the most likely cause of these failures?

Answer options: ✅ Insufficient pipe support allowing for excessive thermal expansion and sagging.

• Incorrect solvent cement used for joining PP-R pipes.
• Exposure to direct ultraviolet (UV) light.
• Over-tightening of mechanical fittings causing stress cracks.

Correct answer: Insufficient pipe support allowing for excessive thermal expansion and sagging.

Explanation: PP-R pipe has a relatively high coefficient of thermal expansion. Inadequate support for hot water lines can lead to significant sagging and stress on joints as the pipe expands and contracts, eventually causing leaks. While other issues can affect PP-R, sagged pipe in a hot water system directly points to thermal expansion and insufficient support as the primary cause.