A barrel strainer used during drafting must be submerged at least how many feet to prevent vortex?

• A. 2 feet
• B. 1 foot
• C. 4 feet
• D. 6 feet

Answer: (A)

Submerging the barrel strainer at least two feet below the water surface prevents the suction vortex from forming at the intake. When the strainer sits close to the surface, the water around it tends to swirl and create a low-pressure center that can pull air into the pump, breaking the prime. Keeping the intake two feet or more below the surface places it in clearer, more stable water and reduces surface disturbances, helping maintain a continuous, air-free water column into the pump. Going deeper than that isn’t necessary for vortex prevention and can increase suction head and potential for drawing up bottom debris, so the minimum of two feet is the practical, reliable depth.