Journeyman Plumber ExamWater Supply SystemsHard
A plumber is installing a hot water recirculation system in a large single-family home. The system includes a circulator pump. Which type of check valve is typically recommended for installation on the discharge side of the recirculation pump to prevent reverse flow and ensure efficient operation?
- ABall check valve.
- BSpring-loaded check valve.
- CSwing check valve.
- DLift check valve.
Show answer & explanationAnswer & explanation
Correct answer: B. Spring-loaded check valve.
A spring-loaded check valve is generally preferred on the discharge side of a recirculation pump. Its spring mechanism ensures a positive seal against reverse flow, even with low differential pressure, and helps prevent 'ghost flow' or thermosiphoning when the pump is off, which would defeat the energy-saving purpose of the recirculation system.
Why the other options are wrong
- A. Ball check valves can be used but may not be as effective as spring-loaded types in preventing low-flow reverse or thermosiphon flow in recirculation systems.
- C. Swing check valves require a certain amount of flow to close fully and may not prevent low-flow reverse or thermosiphon flow effectively in a recirculation loop.
- D. Lift check valves are designed for vertical flow and may not seal effectively against low pressures or prevent thermosiphon flow in a horizontal recirculation line.
Recirculation Pump Check Valve
A valve installed on the discharge of a hot water recirculation pump to prevent water from flowing backward through the pump when it is off, ensuring efficient operation and preventing heat loss due to thermosiphoning.
- Prevents thermosiphoning (ghost flow).
- Ensures pump efficiency.
- Spring-loaded types are most effective for positive shut-off.
Memory trick: Recirculation pump: Spring-loaded check, keeps the hot water in check.