10 Questions You Should to Know about Right Angle Check Valve

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

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.

You will get efficient and thoughtful service from Huade Hydraulic.

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?”

For more information, please visit Right Angle Check Valve.

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:

(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  .

If you want to learn more, please visit our website Electromagnetic Relief Valve.

Ask The Experts: What Is A Check Valve? 

Most valves are operated by a human, air pressure, or even electricity. When these elements are unavailable or fail to perform, a check valve keeps on working. A check valve is intended to automatically shut off when pressure reduces or changes direction so that fluids or gasses are only able to travel in one direction. Another way to say this is that check valves prevent backflow. Inside a check valve, there is either a disc or ball that moves away from the inlet when pressure is applied. This pressure is created by the flow of a fluid or gas. The disc or ball moves back and blocks the inlet when pressure comes from the opposite direction. The components of a check valve usually included the body, seat, disc, and cover.

What to expect

Pima Swing Check Valve Flow Direction; What is a check valve?
Flow from left to right in a swing check valve.

You may recall from reading about gate valves and globe valves that normal valve components usually include a bonnet, body, disc, and stem. Check valves do not usually have a stem or variation in bonnets, and body style is not a defining feature. This is a very unique style of valve! Check valves are defined by the type of force that closes the flow. The forces that stop flow in a check valve are back-flow pressure, gravity, and springs.

Swing Check

The most common structure of check valve in the marine industry is the swing check. Typical swing check valves have a fluid that flows straight through it. Inside the valve, there is a disc that is seated over the inlet. When fluid goes in and applies pressure on the disc, the disc is pushed into the open position. When the pressure reduces or backward pressure occurs, the disc is pushed back into its seat in the closed position. This automatically prevents backflow from occurring. 

Lift Check

A lift check uses flow pressure in a similar way to swing checks. Flow pressure moves the disc to the open position, and reducing pressure or changing direction moves the disc to a closed position. The main difference in a lift check is that flow does not go straight through the valve. Instead, it moves upward against the disc and then back down to the outlet. This means that when flow pressure decreases or changes direction, gravity helps push the disc closed and ensures a faster, tighter seal. The changing internal direction of fluid gives more opportunity for build-up of debris and residue, so this style is not recommended for viscous material.

Piston Check

A piston check is very similar in function to a lift check. The big difference is that the disc is spring loaded, meaning that a spring pushes the disc into a closed position. This closes the disc faster, causing less backflow in the line and reduces the possibility of hammer-stop. However, it can also result in a higher amount of pressure reduction since the flow pressure has to both lift the disc and press the spring-loaded piston upward.

Inline Check

Inline check valves are smaller-bodied check valves that are spring loaded. Most inline check valves are intended for vertical installation, though they can be used in any direction. It has a disc or globe inside of it that is forced by a spring to seat in the inlet, stopping backflow. Flow pressure against the disc or globe in the correct direction causes it to open, and when pressure begins reducing, the spring presses it back into a closed position again. This is great when a check is needed and flow is moving in a downward vertical direction because the check does not rely on gravity or solely on backflow pressure to close.

This style is also known as a silent check. The reason for this is that the spring pressure causes it to close gradually and directly as inflow pressure reduces which results in a quieter close. A silent close means less hammer-stop and less vibration, which means pipes and valves last longer.

Wafer Check

Wafer check valves look a lot like butterfly valves at first glance. They are narrow, which makes them great when there isn’t enough room for a bulky valve. Usually with a wafer check valve, there is a minimum back-pressure requirement restriction, which means it may have some seepage in the closed position and allow some backflow. Because of its shape and thickness, it works very well for fluids that are viscous or contain debris.

Choosing your check valve

Check valves come in a myriad of variations. All of them have strengths and weaknesses that must be accounted for when choosing a check valve. Before you choose a check valve, make sure you know the application of the valve. Take into account fluid pressure, consistency of pressure, viscosity of the fluid, and allowable amount of backflow. For example, if you are checking mud, a piston gate valve will probably clog fast and not function well. If you are checking gasoline, a wafer check may allow too much backflow resulting in loss of material from your pumps dumping it. If you are sending sea-water downward through a vertical line, a standard check valve probably won’t stop much. Determine your needs and then check the ANSI ratings of valves before making your final decision.

Other Styles and terms

Earlier we stated that a check valve doesn’t usually have a stem. It should be noted that some check valves, like the Pima bronze scupper, have a gag. This is a stem that is used for throttling a check valve manually, though it’s usually left alone since the check valve should prevent backflow automatically.

You may hear about the cracking pressure of a check valve. This is the minimum amount of pressure required to move the disc off of the seat and allow positive flow through the valve. Determine the minimum backpressure of your line before choosing a check valve that has minimum pressure requirements.There are plenty of other check valve styles that exist or are being developed. For example, scuppers are check valves that are designed to prevent the backflow of sewage, though mechanically they can be very similar to swing checks or, in some applications, wafer checks. A lot of the check valves we didn’t cover here aren’t used for marine purposes or are less common in the marine industry. This doesn’t mean that we don’t sell the other types though! We carry a huge variety of check valves, and if you have questions about these check valves or other types of check valves, feel free to connect with our experts at Tork Systems, Inc. We’re always on standby to share our knowledge and make your job easier.

Ask The Experts: What Is A Check Valve? 

Most valves are operated by a human, air pressure, or even electricity. When these elements are unavailable or fail to perform, a check valve keeps on working. A check valve is intended to automatically shut off when pressure reduces or changes direction so that fluids or gasses are only able to travel in one direction. Another way to say this is that check valves prevent backflow. Inside a check valve, there is either a disc or ball that moves away from the inlet when pressure is applied. This pressure is created by the flow of a fluid or gas. The disc or ball moves back and blocks the inlet when pressure comes from the opposite direction. The components of a check valve usually included the body, seat, disc, and cover.

What to expect

Pima Swing Check Valve Flow Direction; What is a check valve?
Flow from left to right in a swing check valve.

You may recall from reading about gate valves and globe valves that normal valve components usually include a bonnet, body, disc, and stem. Check valves do not usually have a stem or variation in bonnets, and body style is not a defining feature. This is a very unique style of valve! Check valves are defined by the type of force that closes the flow. The forces that stop flow in a check valve are back-flow pressure, gravity, and springs.

Swing Check

The most common structure of check valve in the marine industry is the swing check. Typical swing check valves have a fluid that flows straight through it. Inside the valve, there is a disc that is seated over the inlet. When fluid goes in and applies pressure on the disc, the disc is pushed into the open position. When the pressure reduces or backward pressure occurs, the disc is pushed back into its seat in the closed position. This automatically prevents backflow from occurring. 

Lift Check

A lift check uses flow pressure in a similar way to swing checks. Flow pressure moves the disc to the open position, and reducing pressure or changing direction moves the disc to a closed position. The main difference in a lift check is that flow does not go straight through the valve. Instead, it moves upward against the disc and then back down to the outlet. This means that when flow pressure decreases or changes direction, gravity helps push the disc closed and ensures a faster, tighter seal. The changing internal direction of fluid gives more opportunity for build-up of debris and residue, so this style is not recommended for viscous material.

Piston Check

A piston check is very similar in function to a lift check. The big difference is that the disc is spring loaded, meaning that a spring pushes the disc into a closed position. This closes the disc faster, causing less backflow in the line and reduces the possibility of hammer-stop. However, it can also result in a higher amount of pressure reduction since the flow pressure has to both lift the disc and press the spring-loaded piston upward.

Inline Check

Inline check valves are smaller-bodied check valves that are spring loaded. Most inline check valves are intended for vertical installation, though they can be used in any direction. It has a disc or globe inside of it that is forced by a spring to seat in the inlet, stopping backflow. Flow pressure against the disc or globe in the correct direction causes it to open, and when pressure begins reducing, the spring presses it back into a closed position again. This is great when a check is needed and flow is moving in a downward vertical direction because the check does not rely on gravity or solely on backflow pressure to close.

This style is also known as a silent check. The reason for this is that the spring pressure causes it to close gradually and directly as inflow pressure reduces which results in a quieter close. A silent close means less hammer-stop and less vibration, which means pipes and valves last longer.

Wafer Check

Wafer check valves look a lot like butterfly valves at first glance. They are narrow, which makes them great when there isn’t enough room for a bulky valve. Usually with a wafer check valve, there is a minimum back-pressure requirement restriction, which means it may have some seepage in the closed position and allow some backflow. Because of its shape and thickness, it works very well for fluids that are viscous or contain debris.

Choosing your check valve

Check valves come in a myriad of variations. All of them have strengths and weaknesses that must be accounted for when choosing a check valve. Before you choose a check valve, make sure you know the application of the valve. Take into account fluid pressure, consistency of pressure, viscosity of the fluid, and allowable amount of backflow. For example, if you are checking mud, a piston gate valve will probably clog fast and not function well. If you are checking gasoline, a wafer check may allow too much backflow resulting in loss of material from your pumps dumping it. If you are sending sea-water downward through a vertical line, a standard check valve probably won’t stop much. Determine your needs and then check the ANSI ratings of valves before making your final decision.

Other Styles and terms

Earlier we stated that a check valve doesn’t usually have a stem. It should be noted that some check valves, like the Pima bronze scupper, have a gag. This is a stem that is used for throttling a check valve manually, though it’s usually left alone since the check valve should prevent backflow automatically.

You may hear about the cracking pressure of a check valve. This is the minimum amount of pressure required to move the disc off of the seat and allow positive flow through the valve. Determine the minimum backpressure of your line before choosing a check valve that has minimum pressure requirements.