Length of pipe, fire department connections and the ______ are the three components that make up a dry hydrant.

The correct answer is the strainer because it is an essential component of a dry hydrant system. A dry hydrant is designed to provide a reliable water source for firefighting operations, particularly in rural or remote areas where conventional water supplies may not be readily available.

The strainer is positioned at the end of the pipe that is submerged in the water source, such as a lake or pond. Its primary purpose is to prevent debris, sediment, and large particles from entering the pipeline when firefighters connect their equipment to draw water. This is crucial because allowing debris to enter the system could obstruct flow or damage fire pumps, thereby reducing the effectiveness of the firefighting efforts.

The other components mentioned — the length of pipe and the fire department connections — are also critical, as the pipe facilitates the transport of water and the connections allow firefighters to access that water. However, without a strainer, the functionality and reliability of the water supply system could be severely compromised. The strainer thus plays a key role in ensuring that the water drawn is clean and usable.