What type of valve shall be installed on the discharge side of water meters?

The correct choice, full port valves, is essential for installation on the discharge side of water meters due to their design that allows for minimal resistance to flow. Full port valves have a larger opening that matches the diameter of the pipe, which ensures that water can flow unimpeded. This feature is crucial in preventing pressure drops and allows for accurate meter readings, making them ideal for systems where maintaining flow rate is important.

In contrast, while ball valves also provide a good flow rate, their size may not always match the diameter of the pipe they are attached to, potentially leading to restrictions depending on the particular design. Gate valves, although good for on/off service, can create turbulence and pressure loss due to their design, which is not optimal for the discharge side of a meter. Lastly, check valves serve a different purpose entirely, as they prevent backflow in the system rather than regulating the flow rate from the meter.