difference between check valve and backflow preventer

Don’t Get Crossed Up: The Difference Between Check Valve and Backflow Preventer

Last Updated on September 1, 2023

Water is vital for everyday use, and installing valves to prevent backflow can ensure its uninterrupted supply. Two such valves are the backflow and check valves, which may seem similar but have distinct differences.

A backflow valve, also known as a backwater valve, is designed to prevent sewage and wastewater from flowing back into the clean water supply. This device shuts off the pipe when there’s a sudden drop in water pressure, like when the water main breaks.

In contrast, a check valve is a one-way valve that permits water flow in one direction and prevents it from flowing in the opposite direction. It is commonly used to prevent water from flowing back into a sump pump or well.

Get an in-depth understanding of the differences between backflow and check valves so you can decide which one works best for your system. With this blog post as your guide, you can confidently select the right valve.

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Function and Design

Backflow valves and check valves are two types of valves used to prevent the reverse flow of fluids, gasses, or other substances in a pipeline or piping system. The primary function of both types of valves is to ensure that the fluid flows in the desired direction and prevent any backflow that could contaminate the system or cause damage.

A check valve, also known as a non-return valve or one-way valve, allows fluid or gas to flow in one direction while preventing backflow in the opposite direction.

Backflow valve

The design of a check valve typically includes a spring-loaded disc or ball that opens and closes based on the flow direction of the fluid.

When the fluid flows in the intended direction, the disc or ball is pushed open, allowing the fluid to pass through. When the flow stops, the disc or ball closes, preventing backflow.

In case of backflow, a backflow valve, also called a backwater valve or a backflow preventer, shuts off the flow completely. The design of a backflow valve includes a spring-loaded mechanism that automatically closes when the flow direction changes, thus preventing any reverse flow.


Different types of backflow valves and check valves are available, each with unique features and applications.

Types of Backflow Valve

  • Automatic Backflow Valve: This type of backflow valve is designed to be self-activating and relies on the force of water to operate. It is commonly installed in areas with high water pressure and does not require manual activation.
  • Manual Backflow Valve: Manual backflow valves require manual activation and are commonly installed in low-pressure areas. They are designed with a hand-operated lever or gate that must be turned or moved to close the valve and prevent backflow.
  • Combination Backflow Valve: Combination backflow valves combine the features of both automatic and manual backflow valves. Depending on the water pressure and flow, they are designed to switch between automatic and manual modes.

Types of Check Valve

  • Swing Check Valve: A swing check valve operates by swinging open and closing on a hinge. It is commonly used in plumbing systems and is designed to allow water flow in one direction while preventing it from flowing back.
  • Lift Check Valve: A lift check valve operates by lifting a disk off the seat to allow water to flow in one direction. When the water flow stops, the disk falls back into place, sealing off the valve and preventing backflow.
  • Ball Check Valve: A ball check valve uses a ball to seal off the valve and prevent backflow. The ball is designed to move away from the valve seat when water flows in one direction, allowing water to pass through. When the water flow stops, the ball returns to its original position, sealing off the valve and preventing backflow.


Both backflow valves and check valves are typically installed at points in the piping system where backflow can occur. Installing these valves is critical to ensure the system’s proper functioning and prevent any potential damage or contamination.

Check valves are usually installed vertically or horizontally, depending on the specific design and application. They can be installed in pipelines, pumps, and other equipment that require one-way flow control.

Check valves should be installed with proper consideration of the fluid or gas flow direction, pressure, and temperature.

Backflow valves are typically installed in low points in the piping system, such as basement floors or below ground level. Installing backflow valves is typically more complex than check valves due to their additional features.

Backflow valves should be installed by a professional plumber or a licensed contractor to ensure compliance with local building codes and regulations.

Pros and cons of each type

The choice between a backflow valve and a check valve depends on the specific application and the level of protection required. Check valves are inexpensive and straightforward to install, making them an excellent option for low-risk applications.

They have a low pressure drop, meaning they do not significantly impede fluid flow in the pipeline. Additionally, check valves have no moving parts, which means they require minimal maintenance and are highly reliable.

Backflow valves are more expensive than check valves and require more maintenance due to their more complex design. However, they offer superior protection against backflow and contamination.

Backflow valves are particularly useful in applications where there is a risk of cross-connection between potable and non-potable water systems, such as in hospitals or commercial buildings. They can also be used to prevent the backflow of hazardous materials in industrial applications.

Which type is best for different situations?

The choice between backflow valves and check valves depends on various factors such as flow rate, pressure, temperature, and fluid characteristics.

Check valves are generally good for low-risk applications where cost is a big deal and preventing backflow is the biggest concern. Examples of such applications include residential plumbing, HVAC systems, and some industrial processes.

Backflow valves are best suited for applications with a higher risk of contamination or pollution, such as in irrigation systems, wastewater treatment plants, and industrial processes involving hazardous materials.

When selecting a valve, it is essential to consider the flow rate, pressure, temperature, and fluid characteristics to ensure the valve is appropriate for the specific application.

The backflow valve and check valve prevent fluid flow reversal in pipelines. Check valves are suitable for low-risk applications where the cost is a significant factor, while backflow valves are more expensive but provide superior protection against backflow and contamination. You can choose either type of valve based on the application and level of protection.

Is a backflow preventer the same as a backflow valve?

Yes, a backflow preventer and a backflow valve are the same things. Backflow preventers are designed to prevent the backflow of contaminated or non-potable water into the clean water supply. They are often referred to as backflow valves or backwater valves. 

When there’s a sudden drop in water pressure like during a water main break, these valves prevent sewage from flowing back into the clean water supply. The terms “backflow preventer” and “backflow valve” are often used interchangeably in the plumbing industry.

Where do you install a check valve?

The specific location of the check valve installation may vary depending on the application. For instance, in a pressure washer, the check valve is installed on the outlet side of the pump to prevent water from flowing back into the pump. At the same time, in a chromatography system, it may be located at various points in the fluid path to prevent backflow. 

In an ultra-performance liquid chromatography system, the check valve is installed in the binary solvent manager (BSM) module, which controls the flow of solvents to the system. Sometimes, a check valve may be installed in the main sewer line to prevent wastewater backflow, which could occur during heavy rain or flooding.

How do I know if I have a backflow valve?

If you’re unsure if your home has a backflow valve installed, there are a few ways to check.

First, check with your local water utility provider or plumbing professional. They should be able to tell you if your home is equipped with a backflow preventer valve and, if so, where it is located.

Second, look for a valve located between your water meter and your home. This valve is typically installed in line with the meter box, low to the ground, and sometimes behind bushes. If you find a valve at this location, it may be a backflow preventer valve.

If you’re unable to locate a backflow preventer valve in your home, it may be time to consider having one installed.

Can we use a check valve in both directions?

Check valves that allow fluid or gas to flow in only one direction and prevent backflow in the opposite direction. Depending on the type of check valve, it may be able to function in either a horizontal or vertical position, but it will not work effectively in both directions.

In general, check valves are engineered to work best in a specific direction, and using them in the wrong direction can cause them to malfunction or fail. Generally, swing check valves work best in a horizontal position, while vertical lift check valves, which use spring tension to close, work best in a vertical position.

It’s important to consult the manufacturer’s specifications and recommendations for the specific type of check valve being used to ensure it is installed in the correct orientation and direction.

Protect Your Plumbing System with Backflow and Check Valves

Backflow valves and check valves are essential in ensuring plumbing systems’ safe and effective operation. Both types of valves are designed to prevent the backflow of fluids or gasses, which can contaminate the clean water supply or damage the plumbing system.

Proper installation, inspection, and maintenance of backflow and check valves are crucial to ensure their effectiveness. A licensed plumber who is well-versed in local building codes and regulations is recommended to install these valves.

Regular inspections by a licensed plumber are crucial to ensure that the valves are operating correctly, are not damaged or obstructed, and detect any signs of wear or corrosion.

The choice of the appropriate valve for the application is also essential. There are various types of backflow valves and check valves, and the selection will depend on the specific requirements of the plumbing system.

Selecting the appropriate valve and ensuring it is installed correctly is crucial to prevent contamination of the clean water supply and damage to the plumbing system.

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Last update on 2023-12-05 / Affiliate links / Images from Amazon Product Advertising API

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