Check valves are often considered the most “quiet” yet essential components in a piping system. Their primary function is to prevent backflow and safeguard pumps, compressors, and the overall stability of the system. However, in real-world applications, poor sealing—commonly referred to as “leakage”—is one of the most frequent and frustrating issues encountered in check valve operation.

 

When a check valve fails to seal properly, it can reduce system efficiency, trigger pressure fluctuations, cause water hammer, and even damage critical equipment. This article breaks down the technical causes behind check valve leakage and offers practical diagnostic and corrective measures to help you quickly identify and resolve sealing problems, even under challenging operating.

 

1. Why Does a Check Valve Fail to Close Properly? Common Causes Explained

 

1. Presence of Particles or Solid Impurities in the Medium

Solid particles can become trapped between the disc and the seat, preventing full contact and causing slight or even noticeable leakage.

 

Typical signs include:

● Significant leakage at small opening positions

● Leakage decreases after cleaning

 

2. Disc Wear or Seat Damage

Frequent cycling, corrosive media, or high-velocity flow can wear the sealing surfaces, resulting in scratches, pits, or deformation.

This issue is especially common in high-temperature steam systems.

 

3. Incorrect Installation Direction or Insufficient Tilt Angle

Although it may sound like a basic mistake, incorrect installation still occurs on many job sites.

Since check valves rely heavily on gravity and flow direction, improper installation prevents the disc from returning to its closed position smoothly.

 

4. Flow Velocity Too Low to Create Adequate Differential Pressure

A check valve opens through fluid flow. When the flow rate is too low, the disc may flutter or fail to close completely, leading to leakage.

 

Common scenarios include:

● Insufficient straight-pipe length

● Frequent pump start/stop

● Poorly designed low-flow systems

 

5. Disc Sticking or Hinge Mechanism Not Operating Smoothly

In swing check valves, rust, corrosion, or lack of lubrication at the hinge pin or disc connection may cause sticking, preventing full closure.

 

6. Thermal Deformation of Sealing Surfaces Due to Temperature Fluctuations

In high-temperature conditions such as steam service, thermal expansion and contraction can slightly deform sealing surfaces, resulting in an imperfect seal.

 

2. How to Quickly Determine If a Check Valve Is Not Closing Properly?

 

1. Abnormal Pressure Gauge Readings

If the inlet pressure remains stable while the outlet pressure gradually rises, backflow caused by check-valve leakage is the most likely reason.

 

2. Pipe Vibration or Light Knocking Sounds

This indicates that the disc is oscillating at high frequency, often due to insufficient flow velocity or a loose disc assembly.

 

3. Inspection via Bypass or Drain Port

Some systems are equipped with a drain or bypass connection, which allows direct observation for signs of backflow.

 

4. Internal Inspection by Disassembling the Valve

The most direct—and often the most effective—method, usually performed during scheduled shutdown and maintenance.

 

3. Effective Solutions for a Check Valve That Fails to Close Properly

 

1. Clean the Sealing Surfaces and Remove Internal Debris

Ideal for mild leakage caused by particulate media.

After cleaning, check the strainer and upstream pipeline for blockages to prevent recurrence.

 

2. Regrind or Replace the Disc and Seat

Applicable when the sealing surfaces show minor wear.

If the damage is significant, replacing the entire disc assembly—or even the valve—is recommended.

 

3. Increase Flow Velocity or Adjust Operating Conditions

Increase system pressure when flow velocity is too low

Optimize pump operating mode

Extend the straight-pipe length upstream when possible

 

4. Select a Check Valve Design That Fits the Application

Each check-valve type has its ideal working conditions:

● Lift Check Valve: Best for vertical installation and high-pressure systems

● Swing Check Valve: Suitable for low pressure, large diameters, and clean media

● Dual-Plate (Wafer) Check Valve: Ideal when straight-pipe length is limited

● Butterfly Check Valve: Suitable for large-diameter, low-pressure applications

 

If the valve type does not match the medium or operating conditions, maintenance alone may not completely resolve the issue.

 

5. Inspect the Hinge, Pin, and Moving Components

Remove any sticking or corrosion; replace moving parts when necessary.

 

4. How to Reduce the Likelihood of Check Valve Leakage

 

1. Proper Valve Selection Is Essential

Nearly 80% of check valve failures come from incorrect selection rather than quality issues.

 

Key factors to consider include:

● Presence of particles in the medium

● Expected flow velocity range

● Temperature and pressure fluctuations

● Installation orientation

 

2. Install a Strainer or Upstream Protection Device

This helps minimize the amount of debris entering the valve body.

 

3. Conduct Regular Maintenance and Inspections

Especially important for systems involving high-temperature steam, corrosive media, or frequent start–stop operations.

 

4. Choose a Reliable Manufacturer

High-precision machining leads to better disc–seat alignment, improved sealing, and more stable long-term performance.

 

5. Conclusion

 

Check valve leakage may seem straightforward, but it actually involves multiple factors, including the medium, valve design, flow velocity, installation orientation, and sealing materials. By applying the diagnostic methods and solutions discussed in this article, most issues can be quickly identified and resolved.

 

For complex or recurring leakage problems in your projects, feel free to contact Dervos Valve for expert guidance on valve selection, inspection services, or system optimization solutions.

 

Q&A – Common Questions

 

Q1: Can a check valve with minor leakage continue to be used?

Short-term use is possible, but prolonged operation may cause backflow, water hammer, or equipment damage. It is recommended to address the issue as soon as possible.

 

Q2: Can a check valve achieve absolute zero leakage?

Metal-seated valves rarely achieve absolute zero leakage. Soft-seated valves can approach zero leakage, but it is essential to ensure compatibility with temperature and corrosive conditions.

 

Q3: Can increasing the valve size reduce leakage?

No. An oversized valve may cause insufficient flow velocity, leading to valve disc vibration and incomplete closure.

 

Q4: Which type of check valve is better for media containing particles?

Lift check valves or designs tolerant to particles—such as guided disc structures—are recommended. Installing a filter upstream is also advised.