Final answer:
After completing a gas system installation, a gas fitter must conduct a pressure test, inform the homeowner, and file a report with the local gas authority.
Step-by-step explanation:
When a gas system installation has been completed, a gas fitter must conduct several important steps to ensure the safety and compliance of the installation. The most critical step is to conduct a pressure test to ensure that there are no leaks and that the system can handle the gas pressure safely. It's also important to inform the homeowner of any necessary information regarding the operation and maintenance of the gas system. Lastly, the gas fitter is typically required to file a report with the local gas authority to document that the installation has been completed according to code and to establish a record of the work done.