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Sat 17 Oct 2020

What is a non-return valve used for?

A non-return valve, also known as a check valve, clack valve, one-way valve or retention valve, is designed to allow fluid to flow in one direction only, therefore preventing the liquid or gas from flowing back upstream of the valve. In this guide, we take a look at how a non-return valve operates, and what a non-return valve is used for, including some of the applications in which you might find one.

What is the function of a non-return valve?

A non-return valve’s functions include preventing reverse flow, protecting equipment, ensuring system efficiency, avoiding mixing or contamination, and enhancing safety. It is essential for maintaining desired flow direction, preventing damage, and maintaining system integrity.

How does a non-return valve work?

A non-return valve usually only has two openings in the body, with a closing member situated between them. When the fluid enters the valve its pressure holds the closing mechanism open. If the fluid attempts to flow back through the valve in the wrong direction, the closing member is forced back over the entrance of the valve preventing any flow.

Non-return valves work automatically, which means that most are not controlled by a person or an external control but by the media flow itself. Depending on exactly what a non-return valve is used for, where it is used, the media flow and the budget available, there are a variety of different types of designs to select from according to the specific application. Types of non-return valves include those designed using a diaphragm, a swing or tilting disc, a stop, a lift, or a ball non-return valve.

Which applications is a non-return valve used for?

Non-return valves are used in a number of different applications, particularly pumps, industrial processes and domestic uses.


Many pump applications include non-return valves to prevent backflow on the pump head on both the inlet and outlet lines. For example, the feed pumps for steam boilers would usually have a check valve fitted, as well as metering pumps, used to maintain a flow rate at a specific outlet pressure. They are also found in chromatography, which is a laboratory purification method for separating out components of a mixture.

Industrial processes

Fluid and processing systems, such as those found in power plants and pharmaceuticals, as well as fuel systems on transportation, commonly use non-return valves within their pipeline systems. An example of what a non-return valve is used for in the nuclear industry could include within the dump lines, in the nitrogen feed system and in areas where water control systems are used.

Non-return valves are used in fuel injection systems; the injectors are simple check valves which are designed to work with a high opening pressure and would be found in aircraft fuel systems as well as on spacecraft where the launch vehicle would use include them in the propulsion propellant control. 

Domestic uses 

Home heating systems, sprinkler systems and inflatable mattresses all use non-return valves. In some cases, the non-return valve can be a critical safety feature. For example, to prevent contaminated, used water from re-entering a domestic water supply. 

INOXPA non-return valves from BM Engineering

The INOXPA is a non-return valve that’s designed specifically for processing industries, preventing both a loss of the pump prime and water hammer. Used widely in food processing, pharmaceutical, oil and chemical industries, the INOXPA non-return valve is available for use with Tri-Clamp, DIN 11851, RJT, weld OD and weld DIN connections. INOXPA are renowned for its work in hygienic industry sectors, with a focus on stainless steel processing pumps, valves, and other components used in this arena. 

A non-return valve is used for what many consider to be basic and standard backflow prevention requirements within any processing system, but the consequences of using a check valve which is not up to the job and not designed for the specific application or industry can be catastrophic. If you are looking for advice on which design or style of non-return valve would work best in your application, contact BM Engineering on 0141 762 0657.

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