Which valve is installed at frequent intervals to allow for the shut-off of small sections of water main?

The isolation valve is specifically designed to be installed at frequent intervals along water mains to enable the shut-off of small sections when needed. This type of valve allows for maintenance or repairs to be conducted in a localized area without disrupting the entire water supply system. By isolating a section of the pipeline, water can continue to flow through unaffected areas, minimizing service interruptions for customers.

Isolation valves are generally operated manually or automatically and are essential for ensuring that maintenance work can be performed safely and efficiently. They also play a crucial role in emergency situations, allowing operators to quickly isolate sections of the system to address leaks or other issues.

In contrast, a check valve is primarily used to prevent backflow and ensure that water flows in one direction. A pressure relief valve is designed to release excess pressure within a system to prevent damage. A ball valve, although useful for shutting off flow, tends to be used for on/off control rather than periodic section isolation along a lengthy pipeline. Therefore, while all these valves serve important functions, the isolation valve is the most suitable for the specific need of segmenting water mains for maintenance and control purposes.