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Check valves prevent reverse flow of fluids and gases within a pipeline system. They are designed to allow fluid to flow one way through the pipeline. Due to the simple design, check valves generally operate without automation or human interaction and instead rely on the flow velocity of the fluid to open and close. You can learn more in our [check valves guide](/web/content/discovery/ideas-and-advice/check-valves-guide).

**How do they work?**

Check valves are flow sensitive and rely on the line fluid to open and close. The internal disc allows flow to pass forward, which opens the valve. The disc begins closing the valve as forward flow decreases or is reversed, depends on the design. Construction is normally simple with only a few components such as the body, seat, disc and cover.

**Check Valve types**

There are several types of check valves for just about any application. Some of the more popular types include:

● Ball

● Dual plate

● Double door

● Spring assisted inline

● Nozzle

● Piston or lift

● swing checks

As with other types of valves, speciality check valves can be found for special applications.

Check valves are found in just about any type of facility from industrial plants and homes.



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Check Valves | Non-return Valves | RS

Check Valves

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Fischer Check Valves | RS Components

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Legris Check Valves | RS Components

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Parker Check Valves | RS

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SMC Check Valves | RS

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Double Check Valves | RS

All check valves are essentially used to prevent the reverse flow (or backflow', i.e. in the opposite direction to that intended) of fluids and gases through a pipeline system.A double check valve is a device designed to help keep your water supply clean and untainted by implementing this very rule, but provides certain key advantages over a single check valve.<h2>How does a double check valve work?</h2><ul><li>A double check valve is an in-line device for prevention of backflow, consisting of two single check valves laid out in sequence</li><li>Note that double check valves should not be confused with two-way check valves (such as those used in air braking systems, which work by selecting the higher pressure of two input sources)</li><li>The fact that the double check valve features two valves arranged in sequence means that the device can still operate functionally, even if one check valve somehow becomes jammed open in use</li><li>The closure one valve also lowers the overall the pressure differential across the other</li><li>This in turn means that the double check valve can create a more reliable seal, which helps to prevent even minor leakage back through the system in the wrong direction</li></ul>Double check valves are very common features of many modern backflow and back siphonage prevention systems, such as those found in everyday domestic/workplace equipment such as combi boilers, fire sprinklers and lawn irrigation networks.Double check valves are less commonly used as standalone backflow prevention devices in higher-hazard applications, though, where an even more robust type of check valve system is often required in order to comply with industry codes and regulations.

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Single Check Valves | RS

Single check valves are designed to offer protection against backflow in fluid category 2 applications. Fluid category 2 is where where there may be an impairment in aesthetic quality of the fluid due to a change in temperature or the presence of substances or organisms causing a change in its taste, odour or appearance. An example of this type of fluid is the waste coming from a mixer tap hose of an appliance such as a washing machine or dishwasher. The single check valve is fitted to the appliance hose to prevent this waste water from contaminating the drinking water supply.

Parker Check Valves

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