What is the purpose of a pump warm-up line?

• A. To keep the secondary pump hot; it goes around the check valve
• B. To increase flow rate
• C. To reduce power consumption
• D. To vent air from the system

Answer: (A)

A pump warm-up line is used to keep the secondary pump hot by circulating hot fluid around the pump when it isn’t running. By routing the loop around the check valve, the line creates a bypass path that allows continuous circulation through the pump itself, even if the main flow path is blocked. This keeps the pump and its seals lubricated and warms the bearings, reducing wear and avoiding thermal shock when you start the pump again.

This isn’t primarily about increasing flow rate, and it doesn’t reduce power consumption in a meaningful, system-wide way. It also isn’t a venting line, so its purpose isn’t to remove air from the system. Its main role is to maintain temperature and readiness of the secondary pump for smoother, longer life.