Final answer:
It is essential to purge each branch line in a piping system to remove air, gas, or contaminants that could impact water quality and pressure, especially following changes to the system, such as replacing lead pipes with copper to prevent lead poisoning.
Step-by-step explanation:
Yes, it is necessary to purge each branch line in a piping system to ensure that no air, gas, or other contaminants are trapped within the pipes, which could affect water quality and pressure. In the context of replacing lead pipes with copper pipes to prevent lead poisoning, the entire system must be purged after installation. Copper is a safe and durable material that is commonly used for plumbing, but any change to the plumbing system requires a thorough purge to clear out debris from the installation process and to ensure proper water flow.