Which reservoir in an air brake system is designed to collect and drain moisture and oil from the compressed air before it enters the service brake system?

Question: Which reservoir in an air brake system is designed to collect and drain moisture and oil from the compressed air before it enters the service brake system?

Answer options:

• Primary service reservoir
• Secondary service reservoir ✅ Wet tank (supply reservoir)
• Emergency reservoir

Correct answer: Wet tank (supply reservoir)

Explanation: The wet tank, also known as the supply reservoir or compressor discharge tank, is the first tank the compressed air enters after the air dryer (or before the air dryer if specified differently). Its primary function is to collect moisture and oil, allowing them to settle at the bottom for drainage before clean, dry air is distributed to the service reservoirs.