Why is a check valve placed in line with the FD connection?

A check valve is placed in line with the fire department (FD) connection primarily to prevent water from flowing back into the engine. This is crucial in maintaining proper operation and safety for the pump system. When a fire apparatus is connected to a water supply, such as a hydrant, the check valve ensures that, once the water is pumped from the source, it cannot reverse its flow back into the engine or any other part of the system. This keeps the pump primed and functioning effectively, safeguarding against potential contaminants from the engine mixing with the clean water supply needed for firefighting.

In addition to preserving water quality and preventing contamination, this mechanism also helps in maintaining the pressure and flow characteristics necessary for effective firefighting operations. Understanding the function of a check valve in this context is essential for any mobile pump operator.