A Comprehensive Guide on Water Check Valves

Water Check Valve

Check valve water-check-valve.jpg

Figure 1: Check valve

A water check valve ensures that water only flows in the desired direction and not backwards. Water flows towards the path of least resistance. While this phenomenon may be ideal for rivers, lakes, and streams, it is not always optimal for water used in residential and commercial buildings. Several types of valves can manage water flow, but most require an outside controller to operate. This article focuses on an automatic option, the water check valve.

Water check valves allow water to flow in one direction only. Stopping backflow can prevent: contaminated water from mixing with drinking water, water pumps from running dry, water waste, flooded basements, and more. Learn more about different types of check valves for water in this article.

Table of contents

Check valves

Check valves operate in a wide variety of applications that require liquid or gas media to flow in a single direction. They have two ports, one as an inlet for the media and one as the output. They do not allow media to flow backwards through the valve, which is why they are also referred to as one way valves or non return valves. This is the primary purpose of check valves, to prevent backflow. Read our check valve article for a more comprehensive understanding!

Check valve for water supply

Backflow preventer vs check valve

Backflow preventers and check valves have the same function and therefore are often mistaken to be the same thing. However, they have one key difference that should never be confused. Backflow preventers are for high-risk applications that require absolutely no contamination of a drinking water source. While check valves can function quite well, they cannot provide the safety measures that backflow preventers do. Read more in our article on backflow preventers versus check valves.

Drinking water

A backflow preventer is necessary when a building is connected to the municipal drinking water supply to avoid contamination. If the water pressure drops, it can cause water to flow back towards the supply, risking contamination of the potable water.

When deciding between valves for a potable water supply application, it's essential to ensure that the valves in question meet the requirements of a regulatory body. Specific requirements vary around the world. Here are a few examples of regulatory institutions:

  • Netherlands: KIWA Water Mark
  • North America: National Sanitation Foundation
  • France: Attestation de Conformite Sanitaire
  • Germany: KTW-W270
  • Great Britain: Water Regulations Advisory Scheme

Well water

A well water system might require a backflow preventer. Before deciding whether or not to install one, be sure to look up the local regulations.

Check valves serve essential functions in well water plumbing systems. First, a water well check valve can keep the water pump primed. At least one check valve before the pump's intake, whether it is a foot valve or an inline check valve, ensures that water stays in the pump and piping when the pump shuts off. Without this water, the pump can burn out when it turns on and operates for longer than a minute.

Second, check valves in well plumbing reduce the effects of water hammer, upthrust, and backspin. These three phenomena occur when water is allowed to freely flow back into the well when the pump shuts off and can damage piping and the motor.

Check valve for garden hose

Installing a garden hose check valve on a water supply faucet is recommended to prevent contaminants from the hose mixing with the building's water system. Quick connect check valves are ideal for this purpose, allowing for easy connection and disconnection of the hose from the faucet or other devices, such as sprinklers or nozzles. When a device is disconnected, the check valve automatically closes, enabling swapping between devices without turning off the water supply. This feature not only makes gardening more efficient but also reduces water waste by preventing water from draining from the hose when switching between devices.

Sprinkler anti-drain check valve

Lawn sprinkler systems that utilize multiple sprinkler heads may experience low-head drainage if there is an elevation change of 2-3 feet between the sprinkler heads. Water in the higher elevated sprinkler heads will naturally flow towards the lowest sprinkler head. This flow leads to puddling around the sprinkler head, allows air into the sprinkler line, and wastes water.

In this situation, two solutions utilize check valves. The first solution is to determine whether the sprinkler mechanism within the sprinkler head has a check valve specifically designed to function with it. If so, the check valve can be installed directly into the sprinkler mechanism. The second solution is to remove the entire sprinkler head casing from the sprinkler line. Next, install an anti-drain valve at the end of the line that connects to the casing. Finally, install the casing to the check valve.

Fire protection sprinkler system check valve

Sprinkler systems for fire protection use check valves to prevent contaminated water from flowing back into the source. Multiple sources supply the sprinkler pipes, so each must have its own check valve to prevent them from backflowing water simultaneously. The National Fire Protection Agency (NFPA) sets regulations for check valves in fire protection sprinkler systems.

Swimming pool check valve

An example of a swimming pool plumbing system with the following components: Pool (A), skimmer (B), check valve (C), pump (D), filter (E), heater (F), check valve (G), auto-chlorinator (H), and return to pool (I).

Figure 2: An example of a swimming pool plumbing system with the following components: Pool (A), skimmer (B), check valve (C), pump (D), filter (E), heater (F), check valve (G), auto-chlorinator (H), and return to pool (I).

Swimming pool pumps circulate and treat pool water to keep the water sanitary. Figure 2 shows that a pump draws water from the pool and passes it through a filter, water heater (if one is installed), and an auto-chlorinator.

A check valve installed before the pump stops water from flowing back into the pool and keeps the pump primed. A check valve before the auto-chlorinator prevents highly chlorinated water from flowing back into the plumbing and damaging components. The pool water sufficiently dilutes the highly-chlorinated water when it returns to the pool. Learn more about swimming pool valves.

Jacuzzi check valve

An ozonator is an optional but common jacuzzi component. This device turns air into ozone and then pumps the ozone into the jacuzzi through a jet. Adding ozone to jacuzzi water is a natural way to help keep the water sanitary and reduce the amount of chemicals required. A jacuzzi check valve is installed in the pipe that takes ozone from the ozonator to the water. This valve stops water from returning through the pipe and damaging the ozonator.

Recirculation system check valve

A hot water recirculation system provides hot water to a fixture almost instantaneously. The system does this by heating water in a heater and then running the water to all hot water fixtures. The alternative would be to turn on the hot water at a fixture and then wait for the water to heat up before it arrives.

Hot water recirculation check valves prevent backflow in important ways. First, a check valve at the cold water supply to the heater prevents hot water, which has higher pressure, from flowing into the cold water supply. Another check valve at the heater's discharge point also prevents downstream water, which is potentially contaminated, from flowing back into the main water supply. Finally, a hot water recirculation system may be composed of multiple zones, especially in the case of multi-unit residential or commercial buildings. There should be a check valve at each point that a zone connects to the main piping of the system. This check valve and a flow control valve will control the amount of water going into the zone and prevent contaminated water from returning to the main piping.


The following information about water check valve materials focuses primarily on the body of the check valve. The material options for seals range from EPDM, FKM, NBR, and more. Concerning the valve discs, plastics and stainless steel are both standard options. Learn more about these options by reading our chemical resistance guide.

  1. Drinking water: Requires careful material selection; common options include lead-free brass, composite/plastic, and stainless steel.
  2. Well water: Common materials include brass, bronze, plastic, and stainless steel. Cast iron is also available for deep wells requiring several check valves.
  3. Garden hose: Typically made of brass or ABS plastic. Brass water check valve is better for long-term use, while ABS is a cost-effective option but vulnerable to sun damage and breaking.
  4. Lawn sprinkler system: Anti-drain check valves are typically buried underground and made of ABS.
  5. Fire protection sprinkler system: Check valve bodies are typically made of ductile iron, and the disc or flapper is stainless steel.
  6. Swimming pool: Check valves are usually made of PVC or ABS, which are compatible with plastic piping. Keep in mind that connecting ABS to PVC requires a special bonding agent.
  7. Jacuzzi: Check valves are typically made of Kynar (PVDF), a type of thermoplastic.
  8. Hot water recirculation system: Brass and stainless steel are excellent material options for a check valve.


What is a water check valve?

A water check valve works by allowing water to flow in one direction but not the other. It opens or closes when specific pressure or flow requirements are met.

Is a water check valve the same as a backflow preventer?

While they serve the same purpose and function similarly, water check valves and backflow preventers are not identical. Backflow preventers are specifically designed to eliminate any chance of contaminated water from entering a drinking water supply.

Does my pool need a check valve?

Check valves are ideal for a pool's water pump to keep it primed. Also, pools connected to a municipal water supply very likely need a check valve as required by law.

What are some bad water check valve symptoms?

Some bad water check valve symptoms include low water pressure, water hammer, irregular water flow, and water backflow in the reverse direction.

How to test a water check valve?

To test a water check valve, close the water supply valve, turn on a faucet to drain the water, disconnect the valve, check for debris, and blow air through the valve in both directions.