What is essential for a check valve to function properly?

For a check valve to function properly, it is crucial that it is installed in a manner that allows for closure by gravity. Check valves are designed to prevent backflow in piping systems by automatically closing when fluid attempts to flow in the reverse direction. If the valve is not installed correctly, it may not close effectively, leading to potential leaks or contamination of the system.

By ensuring that the check valve can close by gravity, the design utilizes the natural force to facilitate proper sealing when no forward flow is present. This typically means the valve should be installed in a horizontal position, although there are some designs that can be installed vertically depending on the specific application and manufacturer guidelines.

The other options, such as requiring a specific angle of installation, vertical-only installation, or the valve being larger than the pipes it connects to, do not directly address the fundamental operational requirement of a check valve to prevent backflow effectively through proper closure.