What is the purpose of activating the primer control?

The purpose of activating the primer control is primarily to allow water to enter the pump. When a fire apparatus is being prepared for operation, it is crucial that the pump be primed to establish a proper vacuum, enabling it to draw water into the pump from the source, whether that be a hydrant, a tank, or another water supply. The primer removes air from the pump, which is essential in creating the necessary pressure difference that allows water to flow into the pump chamber.

By doing this, the pump can effectively begin its operation and deliver water to the fire hoses or other firefighting equipment as needed. This process is crucial for ensuring a prompt and effective response in emergency situations where time is of the essence.