What is the function of a clapper valve in a standpipe system?

A clapper valve in a standpipe system serves the essential function of preventing backflow of water. Its design allows water to flow in one direction while effectively blocking the reverse flow. This is particularly important in firefighting scenarios, as it ensures that water supplied to the fire area does not return to the supply source, maintaining the integrity and pressure of the overall system.

Without the clapper valve, there is a risk of water returning to the system, which could lead to contamination of the water supply or reduced effectiveness of the firefighting efforts. By preventing backflow, the clapper valve is crucial in ensuring that the standpipe system functions optimally, delivering water where it is needed without compromising the flow or pressure.

While the other options present important aspects of firefighting systems, they do not capture the primary role of the clapper valve. This functionality is vital in maintaining a safe and effective water supply during fire emergencies.