The primary purpose of installing a check valve before an intelligent water meter is to prevent backflow. Specifically, the check valve serves the following functions in the water meter:

1. Preventing Backflow Contamination: Without a check valve, water in the pipes might flow backward during pressure changes, bringing contaminants back into the water supply system and polluting the entire network.

2. Protecting Equipment: The check valve prevents the reverse flow of water from impacting the water meter and subsequent pipes and equipment, thereby extending their service life.

3. Ensuring Accurate Measurement: Backflow can cause inaccurate readings on the water meter. Installing a check valve ensures that the meter only records the forward flow of water, guaranteeing the accuracy of the water charges.

4. Complying with Regulations: Many local water supply regulations and standards require the installation of a check valve before the water meter to ensure the safety and hygiene of the water supply system.

Therefore, installing a check valve before an intelligent water meter is a crucial measure to protect the water supply system, ensure water quality, and maintain accurate measurement.