What type of hydrant has the barrel filled with water only when the main valve is open?

• A. Wet Barrel Hydrants
• B. Floating barrel hydrants
• C. Dry Barrel Hydrants
• D. Freeze-proof hydrants

Answer: (C)

In hydrant designs, where water is stored when the hydrant is idle is the key difference. In a dry barrel hydrant, the barrel is kept dry and the water stays in the underground main until you open the hydrant. When the main valve is opened, water flows into the barrel and out the outlets. That means the barrel fills with water only after you open the valve. Wet barrel hydrants, on the other hand, keep water in the barrel at all times, so the barrel is already full even with the valve closed. Freeze-proof hydrants are typically a dry barrel type designed to prevent freezing by locating the valve below ground. So the described behavior—barrel becoming filled only when the main valve is opened—matches a dry barrel hydrant.