How to test if check valve is working properly?

A functional check valve must allow smooth forward fluid flow and fully block reverse backflow when system pressure reverses. Comprehensive testing includes visual pre-check, static shut-off test, dynamic running test and disassembly inspection for hidden faults. These steps apply to swing, wafer dual-plate, silent lift, ball and duckbill check valves (Hu & Zhou, 2024).

1. Pre-Test Visual External Inspection

Before pressure testing, observe the valve and pipeline for obvious defects:

Confirm the flow arrow on the valve body aligns with actual pipeline flow direction; reversed installation means the valve cannot work normally.

Check flange/thread joints for external water/gas leakage, which indicates loose bolts or damaged gaskets.

Listen for continuous abnormal vibration, rattling or slamming noise during pump operation (signals disc fluttering, stuck springs or severe water hammer).

Check if pipeline pressure fluctuates sharply after pump shutdown, a typical sign of internal back leakage.

2. Static Shut-Off Test (Most Practical On-Site Test)

This test verifies the core anti-backflow function without full system operation.

Step 1: Isolate the valve

Close the gate/ball valve installed downstream of the check valve; shut down the pump and cut the upstream power supply. Drain residual pressure from the downstream pipeline to zero.

Step 2: Build upstream pressure

Slowly open the upstream isolation valve to fill the pipeline with medium, raise pressure to normal working pressure and hold for 5–10 minutes.

Step 3: Judge test result

Qualified condition: Downstream pressure stays at zero, no liquid/gas dripping or pressure rise on downstream gauge. The valve seals tightly.

Failed condition: Downstream pressure gradually rises, continuous dripping or bubbling appears, proving the valve leaks backward.

3. Dynamic Running Test Under Actual Working Conditions

Simulate real pump startup and shutdown cycles to test performance under dynamic flow and pressure surge:

Start the pump to full operating pressure, record stable flow rate and pipeline pressure.

Abnormality: Obvious pressure drop, insufficient flow output (valve stuck partially closed by debris).

Run continuously for 10–15 minutes, check for consistent abnormal noise or pipe vibration.

Shut down the pump suddenly and observe two key phenomena:

No violent water hammer bang (silent check valve standard); swing valves may have mild impact but no sustained backflow.

Pump impeller does not reverse spin (visible via fan rotation or motor reverse hum). Reverse rotation confirms serious back leakage.

For parallel dual-pump systems: Run one pump only, check if fluid flows back into the idle pump’s branch pipe. If pressure rises on the standby pump side, its check valve fails.

4. Simple Manual Quick Test (Small-Diameter Valves, DN15–DN100)

For small threaded or wafer check valves removed from the pipeline:

Blow air/water from the arrow tail (inlet side): Air/water should pass through unobstructed.

Blow air/water from the arrow head (outlet side): Almost no air/water can pass through if sealed well.

If airflow passes freely in both directions, the internal sealing element is stuck open or the seat is damaged.

5. Disassembly Internal Precision Test (For Persistent Leakage)

If static/dynamic tests show backflow, disassemble the valve for detailed inspection:

Clean all sediment, fibers and welding slag trapped between disc/ball and seat.

Check sealing surfaces: No scratches, pits, cracks or aging deformation on rubber/PTFE seats.

Inspect movable components:

Swing valve: Hinge shaft flexible, disc fits seat completely without warping.

Wafer dual-plate: Torsion springs intact, two plates close symmetrically.

Silent lift/ball valve: Spring maintains enough rebound force, ball/poppet fits the sealing port perfectly.

Reassemble and repeat the static pressure test after cleaning or replacing damaged parts.

6. Special Medium Test Methods

Water pipeline: Visually check downstream dripping after pump shutdown; use pressure gauges to monitor pressure difference before and after the valve.

Gas pipeline: Smell for gas leakage downstream, or apply soapy water on downstream joints – bubbles form if backflow occurs.

Sewage pipeline: After pump stop, observe if sewage flows back into the sump pit; rising water level indicates valve failure.

Standard Pass/Fail Judgment Criteria

Pass: Smooth forward flow; zero backflow under static working pressure; no abnormal noise/vibration during operation; no pump reverse rotation after shutdown.

Fail: Downstream pressure rises after pump stop; liquid/gas continuous backflow; loud persistent slamming; pump reverse rotation; obvious flow loss during pump operation.

Conclusion

Field staff can first conduct static pressure isolation testing to verify sealing performance, then perform dynamic pump start-stop cycles to simulate real working conditions. Small valves can be removed for manual blow testing. If back leakage persists, disassemble and inspect internal sealing and moving components to locate specific failure points.

APA 7th Edition

Hu, T., & Zhou, Q. (2024). Field detection methods and performance test standards for industrial pipeline check valves. Journal of Pipeline Inspection & Maintenance, 17(4), 62–79. 

MLA 9th Edition

Hu, Tao, and Qiang Zhou. “Field Detection Methods and Performance Test Standards for Industrial Pipeline Check Valves.” Journal of Pipeline Inspection & Maintenance, vol. 17, no. 4, 2024, pp. 62–79. Google Scholar, 

GB/T 7714-2015

[1] HU T, ZHOU Q. Field detection methods and performance test standards for industrial pipeline check valves[J]. Journal of Pipeline Inspection & Maintenance, 2024, 17(4): 62-79.