What is the purpose of bypass valves at large gate valves on the water main?

• A. To increase flow rate
• B. To equalize pressure on both sides of the large gate valve
• C. To prevent backflow
• D. To facilitate quick repairs

Answer: (B)

Bypass valves are installed at large gate valves on water mains primarily to equalize pressure on both sides of the valve. When a large gate valve is closed for maintenance or repair, the upstream side can experience a significant pressure increase while the downstream side remains at lower pressure. This pressure imbalance can lead to stress on the valve and the piping system. The bypass valve allows water to flow around the gate valve, equalizing the pressure differences and preventing damage to the system.

This function is crucial because it promotes the safe operation of the valve and maintains the integrity of the water distribution system. By relieving the pressure difference, it also enables a safer working environment for operators performing maintenance activities.