What is the diameter of the 20ft side intake supply line?

The diameter of the 20ft side intake supply line is indeed 4 inches. This size is commonly utilized in fire services to ensure sufficient water flow for various operations. A 4-inch diameter line provides a good balance between flow capacity and handling characteristics, making it an effective choice for connecting to hydrants or larger water sources. This size allows for the adequate volume of water needed during firefighting events, as well as the ability to efficiently maneuver and deploy the line in various scenarios.

Other choices represent different sizes, which may either provide insufficient flow for certain operations or be unwieldy in terms of handling, thus emphasizing the practicality of the 4-inch diameter in adhering to the needs of emergency response operations.