Guide to Check Valves for Fire Protection

Pressure-activated check valves prevent contamination and flooding from water sources used in fire protection systems

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A check valve is a device that permits the flow of semisolids, liquids, or gases in only one direction. Check valves, featured in systems ranging from residential plumbing to pharmaceutical production, often rely simply on changes in pressure to manage flows.

In this article, we&#;ll focus on check valves for fire protection, discussing how they work, the types of check valves, and their benefits in fire sprinkler systems. Additionally, we&#;ll help you understand what components you should look for when selecting a check valve and discuss how to maintain them.

Already know what you need? Feel free to go straight to our check valve product page and selection of grooved riser check valve trim kits.

How does a check valve for fire protection work?

Each fire sprinkler system needs a dependable source of water for immediate use in a fire emergency. Most systems use some combination of gravity tanks, municipal water supplies, and sometimes fire department connections to provide water to sprinkler heads. But while multiple potential water sources provide an extra layer of reliability to fire protection systems, they can also be problematic: drinkable water might be contaminated by water from a fire hydrant, or dirty water from fire sprinkler pipes might flow through nearby streets and into nearby drains. In many other applications, it&#;s simply important that water only goes one way for performance reasons. These include protecting equipment such as pumps and filters from backflow damage, stopping drainage in a fire sprinkler system with elevation changes, providing pressure relief in liquid or pneumatic applications, and more.

Check valves for fire protection prevent the unwanted reverse flow of water, known as backflow, from occurring. Many check valves feature a hinged clapper with a spring, which keeps the valve closed until the water flowing from some water source opens it. These clappers only open in one direction: when these flows reverse (or very nearly stop), the spring presses the clapper against a rubber seat, forming a water-tight seal.

Think of the water on either side of the clapper as the supply side (between the water source and the check valve) and the system side (between the check valve and the rest of the system). When a fire sprinkler head discharges, water is released, decreasing the pressure on the system side. Shortly after, the higher pressures from water stored or pumped from the supply side push open the clapper, and water flows through the system.

How does a check valve for fire protection prevent contamination of potable water?

When multiple water supplies serve the same fire sprinkler system, each must have a check valve.

From the Edition of NFPA 13

16.9.4.1 Where there is more than one source of water supply, a check valve shall be installed in each connection.

Check valves decide which source actually provides the system with a supply of water at a given moment. When multiple water sources are used simultaneously, only the check valve connected to the highest-pressure water source remains open. Imagine you have a system with three water sources at the following pressure ratings, expressed in pounds per square inch (PSI):

Active Water Sources Check Valve Status   100 PSI Fire Department Connection (FDC)
75 PSI Gravity Tank
50 PSI City Water
FDC, Gravity Tank, & City Open Closed Closed Gravity Tank & City Water Closed Open Closed City Water Only Closed Closed Open

(Note: these pressure levels are provided only as illustrations and are not meant to be taken as typical for these water sources.)

When water is supplied from all three sources, only the check valve leading to the fire department connection remains open. Why?

Of these three sources, the FDC delivers the highest water pressure. This supply pressurizes the water on the system side. This increased system-side pressure is greater than the 75 or 50 PSI on the supply side of the check valves connected to the other water sources and, as a result, their clappers close.

To continue with this example, if only the city water and the gravity tank supply water, the check valve to the 75-PSI gravity tank will open, while the city water&#;s check valve stays closed. Only when all other sources are exhausted or closed does the municipal water supply open the check valve and flow into the system.

What are the types of check valves for fire protection and their benefits?

There are four main types of check valves for fire protection:

• Alarm check valve
• Swing check valve
• Grooved check valve
• Grooved shotgun riser check valve
• Backflow preventers comprising multiple check valves

An alarm check valve consists of a spring, a valve clapper, and an alarm port. The alarm port can be used to direct water to a water motor alarm or an alarm pressure switch used to alert nearby personnel to the system&#;s activation or send a signal to a fire alarm control panel.

A swing check valve can act as an alarm check valve for a wet-pipe fire sprinkler system, but only when that valve can sound an alarm.

From the edition of NFPA 13

16.11.3 Waterflow Detection Devices.

16.11.3.1 Wet Pipe Systems.

The alarm apparatus for a wet pipe system shall consist of a listed alarm check valve or other listed waterflow detection alarm device with the necessary attachments required to give an alarm.

Typically, these alarms are sounded by flow switches, which send a signal to local alarms and/or the fire alarm control panel when water flows through system piping.

Grooved check valves are a type of swing check valve for use in systems that have grooved-connecting pipe ends. Many grooved check valves can be used in a vertical or horizontal orientation, allowing them to be used in various configurations with a fire department connection, bypass connection, gravity pressure tank, or pump discharge connection.

A grooved shotgun riser check valve is similar to a grooved check valve but includes pressure gauges to monitor the supply and system pressure. The shotgun configuration, which uses an electric water flow switch and an alarm bell, is only permitted in situations where a water motor alarm is not required. Shotgun riser check valves offer a more compact and economical alternative to an alarm check valve.

Finally, there are backflow preventers that are explicitly designed to prevent the contamination of water supplies. They use check valves and extra fail-safes to make absolutely sure water flows one way and doesn&#;t contaminate potable water supplies. You can read more about them in our other blog: &#;Backflow Preventer vs. Check Valve: What&#;s the Difference?&#;

Do check valves require periodic maintenance?

Yes, check valves require periodic inspections and maintenance. For this reason, NFPA 13 warns against burying check valves or positioning them in areas where they will be inaccessible.

From the Edition of NFPA 25

13.4.2 Check Valves

13.4.2.1 Inspection. Valves shall be inspected internally every 5 years to verify that all of the valve&#;s components operate correctly.

13.4.2.2 Maintenance. Internal components shall be cleaned, repaired, or replaced as necessary in accordance with the manufacturer&#;s instructions.

Alarm check valves and system riser check valves require more frequent inspections. Regular inspections help to verify that the clapper functions properly, that the valve seat is in good condition, and that there aren&#;t any visible signs of corrosion or blockages.

From the edition of NFPA 25

13.4.1.1* Alarm valves and system riser check valves shall be externally inspected quarterly and shall verify the following:

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Additional resources:
Wireline Pressure Control Equipment

(1) The gauges indicate normal supply water pressure is being maintained.
(2) The valves and trim are free of physical damage.
(3) All valves are in the appropriate open or closed position.
(4) The retarding chamber or alarm drains are not leaking.
(5) Where applicable, the valve in the connection to the pressure-type contacts or water motor&#;operated alarm devices are either sealed, locked, or electrically supervised in the open position.

NFPA 25 also requires an inspection of alarm valves&#; internal components every five years.

13.4.1.2* Alarm valves and their associated strainers, filters, and restriction orifices shall be inspected internally every 5 years unless tests indicate a greater frequency is necessary.

Maintenance should be performed by following the guidelines set by the manufacturer. Following an inspection, the manufacturer&#;s guidelines should also be used while returning the system to service.

What&#;s the best brand of check valve? What should I look for?

Every check valve installed on a fire protection system should be FM-approved and/or UL-listed. Listings certify that a check valve is designed to withstand the conditions it&#;ll be exposed to while in use. They&#;re also specifically required by NFPA for check valves on fire sprinkler FDCs and the alarm check valves used with wet-pipe fire sprinkler systems.

From the edition of NFPA 13

16.11.3 Waterflow Detection Devices.

16.11.3.1 Wet Pipe Systems.

The alarm apparatus for a wet pipe system shall consist of a listed alarm check valve or other listed waterflow detection alarm device with the necessary attachments required to give an alarm.

16.12.6 Valves.

16.12.6.1 A listed check valve shall be installed in each fire department connection and shall be located in an accessible location.

In addition, when you&#;re purchasing a check valve for fire protection, you should also consider:

• The size and pressure ratings of your fire protection system
• How easy and fast the check valve is to install
• The quality and construction of the valve&#;s components

QRFS carries UL-listed and FM-approved grooved check valves for pipes ranging from 2 to 6 inches. All of our check valves feature a non-slamming, spring-loaded clapper that forms a water-tight seal against an EPDM synthetic rubber seat. With a durable ductile iron exterior and corrosion-resistant stainless steel clapper, these valves are built to last.

Any of these valves can be installed in a vertical or horizontal orientation. What&#;s more, each can be used as an alarm check valve with a shotgun riser check valve trim kit, available for every check valve we carry.

When you make a purchase from QRFS, you receive quality products at our competitive pricing. We begin processing your order the moment we receive it so we can provide you with the fastest standard delivery possible, generally reaching you in 2-3 business days.

View our selection of grooved, inline, and swing check valves, plus our inventory of grooved riser check valve trim kits.

Questions about this article or our grooved check valves? Call us at +1 (888) 361- or  .

This blog was originally posted by Jason Hugo and Anna Hartenbach at blog.qrfs.com on October 26, , and updated on January 1, . If this article helped you select the right check valve, check us out at Facebook.com/QuickResponseFireSupply or on Twitter @QuickResponseFS.

Check valves, also called non-return valves (NRV), are essential components of any industrial or residential piping system. They are used to prevent backflow, ensuring the proper operation of the system and preventing damage from happening.

Check valves work fairly simply. Pressure from the liquid that is flowing through a piping system opens the valve while any flow-reversal will close the valve. It allows the fluid to flow fully unobstructed in one direction and automatically closes as the pressure is reduced. While that is pretty straightforward, there are different types of check valves, with varying operations and applications. How do you know which type of check valve to use for your job or project? To help you make the right choice, here are some details about the most common types of check valves.

Swing Check Valves

Swing check valves utilize a disc inside the valve to allow or stop the flow of the piping system. As the fluid flows through in the correct direction, the pressure forces the disc to open and stay open. As the pressure decreases, the valve disc closes, stopping the flow of the fluid from reversing. Swing Check Valves come in a wide range of material types, including PVC, CPVC, Clear and Industrial.

There are two types of swing check valves we should look at:

&#; Top-hinged &#; In this type of swing check valve, the disc is attached to the inner top of the valve with a hinge that allows the disc to open and close.

&#; Tilting disc &#; This type of swing check valve is designed in a manner that allows the valve to fully open at lower flow pressure and to close quickly. It does this using a dome-shaped disc that is spring loaded to make the valve close faster than a top-hinged valve. Additionally, the disc in this check valve floats so that the liquid flows on the top and bottom of the disc surfaces.
These types of check valves are most commonly used to prevent flooding in sewage systems and in firefighting applications. They are used in systems that move liquids, gases, and other kinds of media.

Lift Check Valves

Lift check valves most closely resemble globe valves. They utilize a piston or a ball in place of the disc that swing check valves use. Lift check valves are more effective at leak prevention than swing check valves. Here&#;s a look at these two types of lift check valves:

&#; Piston &#; This type of check valve is also known as a plug check valve. It operates by controlling the flow of fluid in a piping system by means of the linear motion of a piston within the valve chamber. Sometimes the piston has a spring attached, which helps it stay in the closed position when not in use.

&#; Ball &#; The ball check valve operates simply using gravity. When there is enough pressure in the flow, the ball is lifted upward, and when the pressure is decreased, the ball rolls down and closes the opening. Ball Check Valves come in a wide range of material types and style types: PVC: Clear and Gray, CPVC: True Union and Compact.

Lift check valves are used in many industries for many applications. You will find them in residential and industrial settings. They are used in the food and beverage industry, oil and gas industry, and the marine industry, to name a few.

Butterfly Check Valves

The butterfly check valve is unique in that its disc actually folds in the middle to allow the flow of liquid. When the flow is reversed, the two halves open back up to seal the valve closed. Also called a dual plate check valve or a folding disc check valve, this type of check valve is good for low-pressure liquid systems as well as gas piping systems.

Stop Check Valves

Stop check valves allow you to start and stop the flow in your piping system. They are different in that they allow you to regulate the flow as well. Stop check valves are basically check valves that have an override control to stop flow regardless of flow direction or pressure. When the pressure is too low, stop check valves will close automatically to prevent backflow. This type of check valve may work using an external control rather than an override control, meaning you can set the valve to the closed position no matter what the flow is doing.

Stop check valves are most commonly used in boiler systems, power plants, petroleum production, and high-pressure safety applications.

Final Thoughts about Check Valves

When it comes to preventing backflow, there is no other option than check valves. Now that you have some information about the different types of check valves, you should be able to decide which one is best for your application.

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