How long may it take to fully open or close a horizontal gate valve?

• A. 5 minutes
• B. 15 minutes
• C. 30 minutes or more
• D. 1 hour

Answer: (D)

The key idea is to operate a horizontal gate valve slowly to avoid creating a dangerous pressure surge in the distribution system. Large gate valves can cause water hammer and flow disturbances if they are moved quickly, so engineers and operators intentionally take a long time to move them through their full travel.

Taking about an hour to go from fully closed to fully open (or the reverse) provides a gradual change in flow and pressure. This slow, deliberate motion allows the system to adjust, helps ensure the valve seats properly without pounding or sticking, and reduces the risk of damaging pipes, meters, hydrants, and other equipment downstream. In smaller timeframes, such as five, fifteen, or thirty minutes, the change in flow can still be rapid enough to cause transient pressures that may stress the system.

In practice, you operate with patience and monitor system pressure as you proceed, but the guidance about a long, hour-long full travel reflects the priority of protecting the distribution network from transient damage while ensuring effective valve operation.