Check valves are essential components in water supply and wastewater treatment systems, ensuring unidirectional flow and preventing backflow. Water supply check valves allow fluid to move in one direction and automatically close when the flow reverses, protecting pipes, pumps, and other equipment from damage. In water distribution networks, they help prevent contamination of potable water during pressure drops or pipe failures. In wastewater treatment, they stop treated water from flowing back into untreated areas, preserving process integrity. By maintaining flow direction and preventing system disruption, water supply check valves play a critical role in protecting water quality and supporting reliable infrastructure.

What Are Check Valves?

A check valve, also known as a non-return or one-way valve, is a mechanical device that permits fluid (liquid or gas) to flow in a single direction while preventing reverse flow. This automatic operation helps protect equipment and maintain system efficiency by preventing issues like backflow, contamination, and pressure surges.

Core Components and Working Principles

Check valves typically consist of two ports: an inlet and an outlet, separated by a movable mechanism such as a disc, ball, or diaphragm. When the upstream pressure exceeds the downstream pressure, the valve opens, allowing fluid to pass through. If the flow reverses or the pressure drops below a certain threshold—known as the cracking pressure—the valve closes, preventing backflow. This closure can be assisted by gravity, spring mechanisms, or fluid dynamics, depending on the valve design.

 

Types of Check Valves for Water Supply Systems

Choosing the right check valve is key to maintaining reliable and efficient water supply systems. Different types are designed to meet specific performance and installation needs.

Swing Check Valves

Swing check valves use a hinged disc that swings open when fluid flows forward and shuts when flow reverses. These valves work best in horizontal pipelines where flow remains steady and turbulence is low. Thanks to their simple design, they create minimal pressure drop and require little maintenance. That makes them ideal for municipal water systems and wastewater treatment plants.

Tilting Disc Check Valves

Tilting disc check valves have a disc that tilts to open and returns to a closed position when flow reverses. Their fast response helps reduce water hammer, which protects the system from pressure shocks. Unlike swing types, they perform well in both horizontal and vertical setups. As a result, they’re often used in pumping stations and clean water systems.

Ball Check Valves

Ball check valves rely on a spherical ball that moves to open or block flow. This simple mechanism handles fluids with suspended solids effectively, reducing the risk of clogging. Because of their durability and low maintenance needs, you’ll find them in sewage systems, wastewater facilities, and various industrial processes.

Lift (Piston) Check Valves

Lift check valves, also known as piston check valves, lift a disc or piston when fluid flows forward and drop it back to stop reverse flow. They handle high-pressure conditions well and can be installed in any orientation. These valves are commonly used in cooling circuits, boiler feedwater lines, and other systems that need tight flow control.

 

Check Valves in Wastewater Treatment: Specialized Solutions

Wastewater treatment systems present unique challenges, including the presence of solids, sludge, and corrosive fluids. To address these, specialized check valves are employed to ensure efficient and reliable operation.

Dual Plate Check Valves

Dual plate check valves, also known as double-disc or wafer check valves, feature two spring-loaded plates that open with forward flow and close swiftly upon flow reversal. This design minimizes pressure drop and reduces the risk of water hammer, making them suitable for space-constrained installations. Their compact and lightweight construction facilitates easy installation and maintenance, while their robust design ensures durability in demanding wastewater environments.

Nozzle Check Valves

Nozzle check valves are engineered for high-performance applications, utilizing a spring-assisted disc and streamlined flow path to provide rapid closure and minimize pressure surges. Their design effectively handles high flow rates and resists water hammer, making them ideal for systems with frequent flow reversals. The smooth, contoured internal passage reduces turbulence and energy loss, enhancing overall system efficiency.

Non-Slam Check Valves

Non-slam check valves are specifically designed to prevent the sudden closure that can lead to water hammer. They employ a spring-assisted mechanism that ensures smooth and silent operation, protecting system components from pressure spikes. These valves are particularly beneficial in vertical installations and systems where maintaining consistent pressure is critical. Their ability to handle varying flow conditions without slamming makes them a reliable choice for wastewater treatment applications.

 

Key Considerations When Selecting Check Valves

Choosing the right check valve is essential for ensuring system efficiency, longevity, and safety. The following factors should be carefully evaluated during the selection process:

Material Compatibility

The valve’s material must be compatible with the media it will handle to prevent corrosion and degradation. Common materials include:

• Ductile Iron: Offers high strength and durability, suitable for potable water systems.

• Stainless Steel: Provides excellent corrosion resistance, ideal for aggressive or corrosive fluids.

• PVC: Lightweight and resistant to a wide range of chemicals, often used in low-pressure applications.

Selecting the appropriate material ensures the valve’s longevity and reliability in specific operating conditions.

Pressure and Flow Rate Requirements

Understanding the system’s pressure and flow characteristics is crucial:

• Operating Pressure: The normal pressure the valve will experience during operation.

• System Pressure: The maximum pressure the system can reach.

• Proof Pressure: The pressure the valve can withstand without permanent deformation.

• Burst Pressure: The pressure at which the valve may fail catastrophically.

Additionally, the valve must accommodate the system’s flow rate without causing excessive pressure drops or flow restrictions.

Installation Orientation

The orientation of the valve installation affects its performance:

• Swing Check Valves: Typically installed in horizontal pipelines; vertical installation requires upward flow direction to function correctly.

• Spring-Assisted Check Valves: Can be installed in both horizontal and vertical positions, offering greater flexibility.

Proper installation orientation ensures optimal valve operation and prevents issues such as backflow or valve failure.

Maintenance Accessibility

Ease of access for inspection and maintenance is vital:

• Placement: Install valves in locations that allow for easy access, avoiding areas that are difficult to reach.

• Clearance: Ensure sufficient space around the valve for maintenance activities, such as cleaning or part replacement.

Strategic placement and accessibility considerations reduce downtime and facilitate routine maintenance, enhancing system reliability.

 

Benefits of Optimized Check Valve Selection

Selecting the appropriate check valve for water supply and wastewater systems offers several key advantages:​

Preventing Backflow Contamination in Potable Water Systems

Check valves are crucial in maintaining the safety of drinking water by preventing the reverse flow of potentially contaminated water into the clean water supply. They act as barriers against backflow, which can occur due to pressure changes in the system, thereby safeguarding public health.​

Reducing Downtime and Pump Damage in Wastewater Plants

In wastewater treatment facilities, check valves protect pumps and other equipment from damage caused by reverse flow and pressure surges. By ensuring unidirectional flow, they help maintain continuous operation and reduce the risk of costly downtime.​

Enhancing Energy Efficiency and Cost Savings

Optimized check valve selection can lead to significant energy savings. For instance, using a 12-inch tilted disc check valve instead of a silent check valve in a system operating at 4,500 gallons per minute can save approximately $464 per year in energy costs. Over the lifespan of a plant, these savings can accumulate substantially.

 

Common Challenges and Solutions

Effective check valve selection and system design are crucial for addressing common issues in water supply and wastewater treatment systems.​

Water Hammer: Causes and Mitigation

Water hammer, or hydraulic shock, occurs when fluid flow is suddenly halted or reversed, causing pressure surges that can damage pipes and equipment. Traditional swing check valves, which rely on gravity and flow reversal to close, can exacerbate this issue. Mitigation strategies include using non-slam check valves, such as spring-loaded, poppet-style valves, which close before reverse flow begins, thereby preventing water hammer. Proper valve sizing and selection are also essential to minimize this phenomenon. ​

Clogging in Wastewater Systems: Valve Design Solutions

Wastewater systems often face clogging due to debris like wipes and fibrous materials. To combat this, specialized valve designs are employed:​

• Swing-Flex Check Valves: Designed to prevent clogging and allow full flow, reducing maintenance time and costs. ​
• Diagonal Single-Vane Impellers (D-max): Offer high efficiency and handle fibrous matter effectively, minimizing clogging risks. ​

Implementing these solutions can significantly reduce downtime and maintenance in wastewater treatment facilities.​

Corrosion Resistance in Harsh Environments

In environments with corrosive fluids, selecting valves made from appropriate materials is vital:​

• Nickel-Aluminum Bronze (NAB): Ideal for salt and brackish water applications due to its corrosion resistance. ​
• Monel Alloys: Provide exceptional resistance in extreme conditions, making them suitable for critical processes.

 

Conclusion

Quality check valves are essential for ensuring safe, efficient, and reliable operation in both water supply and wastewater treatment systems. From preventing backflow contamination and reducing pump damage to improving energy efficiency and minimizing downtime, the right valve selection makes a measurable difference. Whether your application involves clean water, sludge, or corrosive fluids, choosing the right type, material, and installation approach is key. For expert guidance and durable, high-performance valve solutions tailored to your system’s needs, connect with Tanggong Valve Group today.