What characteristic makes the wet tank unique?

The wet tank is unique primarily because it is the one closest to the compressor and is designed to contain the most water. During the compression process, moisture from the air collects in this tank due to the cooling effect as the air is compressed. This tank serves an important function in trapping moisture and preventing it from moving further into the air brake system, where it could freeze or cause corrosion. Thus, the location of the wet tank being nearest to the compressor facilitates the collection of this moisture, making it a critical component in maintaining the overall efficiency and functionality of the braking system.

The size of the wet tank is significant, but it is not exclusively the largest tank in the system. While some tanks may be painted to indicate their function for safety reasons, the blue color does not inherently designate the tank as a wet tank. Lastly, a wet tank does not contain only compressed air; it is a mixture of compressed air and water. Therefore, the defining characteristic of the wet tank is its position in relation to the compressor and its role in moisture collection.