Which type of hydrant has a drain valve that opens when the hydrant is closed?

• A. Wet barrel
• B. Dry barrel
• C. Semi-dry
• D. Combination

Answer: (B)

Drainage that activates when you shut the hydrant is a feature of dry barrel hydrants. In this design, the main valve is located below grade, and when you close the hydrant, a drain valve opens to empty the water from the hydrant and the short section of piping above it. This keeps the hydrant barrel dry and helps prevent freezing in cold weather. Wet barrel hydrants, by contrast, stay full of water in the barrel and do not drain automatically when closed, so they don’t have this automatic drain feature. Semi-dry and combination types have their own drainage arrangements and don’t rely on a drain opening merely because the hydrant is shut.