Why is flushing the supply line important before assembly installation?

Flushing the supply line before assembly installation is essential primarily to ensure cleanliness and prevent blockages. During the installation process, debris, sediment, or other contaminants can accumulate in the pipes, which can lead to operational issues once the system is in place. By flushing the supply line, you remove any particles that could obstruct water flow or affect the functionality of the backflow prevention device. This process helps to mitigate risks associated with compromised water quality, which is crucial for maintaining the integrity of the plumbing system and ensuring safe water delivery.

The other options touch on aspects of maintenance and operational checks, but they do not address the primary concern of removing contaminants effectively. Testing water pressure, checking for leaks, and balancing pressure levels are important tasks in their own right but are not the main purpose of flushing a supply line prior to assembly installation.