In the suction line, what is the purpose of a check valve?

• A. To prevent backflow and maintain prime
• B. To regulate discharge pressure
• C. To filter debris
• D. To connect suction lines

Answer: (A)

The suction-line check valve is there to prevent backflow and keep the pump primed. When water would otherwise siphon back toward the source or lose prime, the check valve closes, stopping reverse flow. That keeps the suction line full of water and ready to deliver—so the pump can develop full suction quickly when starting or changing operating conditions. If water were allowed to flow back, air could enter the suction line and prime would be lost, causing pumping delays or loss of prime.

The other options aren’t the job of a suction check valve: regulating discharge pressure is done by a regulator on the discharge side, filtering debris is handled by strainers or filters, and connecting suction lines is a job for fittings and couplings, not a one-way valve.