A plumber is troubleshooting a hot water recirculation pump that cycles on and off too frequently. The system has a dedicated return line and is equipped with a check valve. What is the most likely cause for the short cycling?

Question: A plumber is troubleshooting a hot water recirculation pump that cycles on and off too frequently. The system has a dedicated return line and is equipped with a check valve. What is the most likely cause for the short cycling?

Answer options: ✅ The check valve in the recirculation line is installed backward or is failing.

• The aquastat setting for the pump is too high.
• There is too much air in the recirculation system.
• The isolation valves on the pump are partially closed.

Correct answer: The check valve in the recirculation line is installed backward or is failing.

Explanation: If the check valve in the recirculation line is installed backward or is failing, it would allow hot water to bypass the controlled path, causing the pump to cycle frequently as it tries to maintain temperature without proper flow. Too high an aquastat setting would keep the pump running longer, and air or partially closed valves would typically reduce flow rather than cause rapid cycling.