The MINIMUM size for a copper water service from the meter or control valve to the building shall be

A 1/2 inch diameter is generally too small for a main water service line, as it may lead to insufficient water pressure and flow for most residential applications. While it can be used for individual fixtures, it does not meet the minimum requirements for a primary service line to a building.

While a 5/8 inch size is slightly larger than a 1/2 inch line, it still fails to provide the necessary capacity for a main service line. This size may restrict water flow, particularly during peak usage times, which could result in inadequate water supply for a household or commercial building.

Although a 1 inch diameter pipe would provide excellent flow and pressure, it exceeds the minimum requirements set forth for copper water service lines. This may lead to unnecessary material costs and could be over-engineering for typical residential needs, where 3/4 inch suffices.