In a fire sprinkler system, what is the purpose of a main drain valve?

The main drain valve in a fire sprinkler system is primarily designed to drain water from the system. This function is crucial for several reasons. When performing maintenance or repairs on the system, it is often necessary to remove water to ensure safety and prevent damage. Draining the system also allows for inspections or testing that require depressurizing or completely emptying the pipes.

In the context of maintenance procedures, the ability to effectively drain the water helps in verifying the condition of various components, including the pipes, valves, and fittings. By draining the water through the main drain valve, technicians can assess for any leaks or corrosion that might exist without the interference of water flow.

The other options, while related to the overall function of fire sprinkler systems, do not accurately describe the primary role of the main drain valve. Testing system pressure and venting air can occur in other parts of the system, but the main drain valve's specific and essential purpose remains focused on the drainage of water.