Check Valves

Verified by Mel Sykes, Industrial Supply Chain Specialist - April 2026

Specification	Details
Types	Swing check, spring check, wafer check, ball check, non-return
Materials	Brass, stainless steel, cast iron, PVC
Standards	BS EN 12334, API 594

## What are Check Valves? Check valves allow fluid or gas to flow in one direction while preventing backflow. They automatically open and close based on the pressure differential across them. ### Types and variants **Swing check:** This type features a hinged disk that swings freely to block reverse flow. Typical dimensions range from DN15 to DN300, with load ratings up to 16 bar. **Spring check:** Uses internal springs to keep the valve closed when pressure drops. Commonly used in smaller pipes, typically DN25 to DN80. **Wafer check:** Designed for inline mounting between flanges. Dimensions range from DN50 to DN400, suitable for pressures up to 16 bar and temperatures below 300°C. **Ball check:** Features a ball that seals against the seat when reverse flow occurs. Commonly used in low-pressure applications like pneumatic systems, with sizes ranging from DN10 to DN25. **Non-return valve:** A general term for any type of valve that prevents backflow, including swing and spring types. They often use EN8 carbon steel or stainless steel grades such as A2-70. ### Materials and specifications Check valves are typically made from brass, stainless steel, cast iron, and PVC. Brass is favoured in low-pressure systems due to its corrosion resistance. Stainless steel variants like A2-70 offer durability and high pressure ratings up to 42 bar. Cast iron models are cost-effective for temperatures below 350°C. Specifications adhere to standards such as BS EN 12334, which defines performance criteria including flow capacity, pressure loss, and mechanical strength. API 594 covers spring-loaded check valves with detailed dimensions and testing requirements. ### Selection criteria Choosing the right check valve depends on several factors: - **Pipe size:** Ensure the valve fits within your system's pipe diameter. - **Pressure rating:** Check valves must withstand maximum operating pressures without failure. - **Flow rate:** Consider the volume of fluid or gas that needs to pass through per minute. - **Material compatibility:** Select materials based on the media being handled, such as corrosive chemicals or high-temperature steam. ### UK suppliers MLC lists verified suppliers from Companies House who meet rigorous quality standards. Suppliers include companies like CBM and BIAFD, offering a range of check valves made to BS EN 12334 specifications. ### Common applications Check valves are used in various industries: **Water treatment:** Prevents backflow contamination in drinking water systems. **Petroleum processing:** Ensures one-way flow in pipelines to maintain system integrity. **HVAC:** Keeps air flowing efficiently in heating and cooling systems. **Automotive:** Controls fluid direction in brake lines and other hydraulic components. **Chemical plants:** Manages process fluids, preventing reverse flow that could cause equipment damage. By selecting the right type of check valve based on your application needs, you can ensure reliable operation and safety in your engineering projects.