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#80 -- Guide to Check Valves for Fire Protection

Posted by Jason Hugo and Anna Hartenbach on 10/26/2017 to Valves
A check valve is a device that only permits the flow of liquids in one direction. Check valves are used in a variety of applications, including many household systems, but for the purposes of this article we’re going to focus on check valves for fire protection.

A consistent, dependable source of water is a necessity to ensure that a fire sprinkler system is capable of quick activation in the instance of a fire emergency – for example, a gravity tank, fire department connection (FDC), or the city water supply. A check valve for fire protection prevents water backflow from occurring. Backflow occurs when water is meant to flow in one direction, but also ends up flowing in the reverse direction. 

Imagine a fire sprinkler system activates during a fire, but the water flowing into the system also has the ability to flow back into the supply tank. That would be counterproductive and create potentially serious health risks! 

In this article, we’ll discuss how a check valve works, the types of check valves, and their benefits. Additionally, we’ll help you understand what components you should look for when selecting a check valve and discuss their maintenance. If you already know what you need, feel free to jump on over the check valve product page.

However, if you’re ready to check (pun!) this out a bit more, keep reading…

How does a check valve for fire protection work? 

Check valves for fire protection only operate with the movement of water. When the temperature rating of a fire sprinkler head is met, causing it to activate, the internal clapper opens so that water can flow through to supply water to the fire sprinkler heads.

Check valves must be installed at every source of water supply so water can only flow in the intended direction. Furthermore, once water enters the pipes of a fire sprinkler system, it becomes non-potable so it’s pertinent to prevent its backflow into the water supply – especially in instances where it’s connected to the city water supply.

From the 2016 Edition of NFPA 13: Where there is more than one source of water supply, a check valve shall be installed in each connection.

Where more than one check valve is used, water comes from the source with the highest amount of pressure (PSI). Once the pressure of that water source drops to a certain level, the check valve with the next highest PSI activates. For example, lets imagine you have a system with three water sources at the following PSI ratings:

Gravity Tank - 100 PSICity Water Supply - 75 PSIFire Department Connection (FDC) 50 PSI
Open ClosedClosed

From the example you can see that when the pressure of the first source drops below the second source, it closes and causes the second source of water to open. When the PSI of the second source of water drops below the third source, it closes and the third source activates. In this instance, the third source of water is the FDC, which is supplied by the fire department pumper trucks.

Although this is the basis of how a check valve operates, the specifics can change with the type of check valve.

What are they types of check valve for fire protection and their benefits? 

The types of check valve for fire protection are: grooved check valves, grooved shotgun riser check valve, alarm check valve, and swing check valves.

From the 2016 Edition of NFPA 13: A listed backflow prevention device shall be considered a check valve, and an additional check valve shall not be required. valves shall be installed in a vertical (flow upwards) or horizontal position in accordance with their listing.

An alarm check valve is somewhat like an all-in-one solution. It consists of a spring, valve clapper, and alarm port. When the alarm port is exposed to water pressure it activates a water motor gong, mechanical bell, or A/V device. Because the alarm port becomes exposed to the incoming water, it provides the ability to install an alarm pressure switch, which can send an alarm signal to the panel.

A swing check valve has the ability to replace an alarm check valve, but it must be used with a flow switch – however, this is only the case for systems that do not require a mechanical alarm. In systems that do require a mechanical alarm, an electric water flow detector can be used to initiate an alarm. 
Grooved check valves are considered 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 position, offering versatility in system design. Because of its flexibility in design, it can be used in a number of configurations with a fire department connection, bypass connection, gravity pressure tank, and pump discharge connection. 

A grooved shotgun riser check valve is similar to a grooved check valve, except supply and pressure gauges are connected to the threaded outlets. The shotgun arrangement it best used in situations where a water motor alarm is not required – using an electric water flow switch and alarm bell instead. In comparison to an alarm check valve, a shotgun riser check valve is more compact and economical. 

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 2017 Edition of NFPA 25: 
13.4.2Check Valves Valves shall be inspected internally every 5 years to verify that all of the valve's components operate correctly. 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 to ensure that there aren’t any visible signs of corrosion or blockages. Any negative findings during an inspection warrant more frequent inspections in the future.

From the 2017 edition of NFPA 25:* 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.

In addition to the alarm and check valves, their inside and related components must be inspected every five years. NFPA 25 provides protocol for the proper inspection of alarm and check valves:

From the 2017 Edition of NFPA 25:
A. The system should be drained for internal inspection of valve components as follows:
(1) Close the control valve
(2) Open the main drain valve
(3) Open the inspector's test valve
(4) Wait for the sound of draining water to cease and for all gauges to indicate 0 psi (0 bar) before removing the handhole cover or dismantling any component.

If maintenance is required for the internal components, it shall be performed by following the guidelines set by the manufacturer. Following the inspection, the manufacturers guidelines should be used to return the system to service.

What’s the best brand of check valve? What should I look for in a check valve for fire protection? 

The most important thing to note is that the quality of a check valve is not dependent on its brand name or lack thereof. The materials and components that make up a check valve are what make it good or “the best.” 

When purchasing a check valve for fire protection, you should consider: the materials it’s made of, how easy and fast it is to install, and the internal components that make it up. The size and pressure ratings must meet the needs of the system that you’re installing. Additionally, check to see if it is FM approved and/or UL listed.

The external body of a check valve is often made of some form of iron, whether it be ductile iron or cast iron. Iron helps reduce damage that can occur in the field. The internal clapper assembly is generally made of stainless steel to fight against corrosion. Check valves made with bronze and E.P.D.M. rubber seating provide a non-stick, leak-tight seal. 

Why choose QRFS for your check valve needs?

At QRFS we have a wide variety of grooved and shotgun riser check valves, ranging from 2 to 6 inches. All of our check valves feature a non-slamming, spring-loaded clapper that prevents backflow and water hammer. They possess a leak-tight, EPDM non-stick seal and can be used in vertical and horizontal orientation. Additionally, all of our check valves are FM approved and UL listed. 

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!

It’s our goal to remain current on industry best practices and NFPA code so we can help you get right information at the right time. At QRFS, we aim to provide you with the newest and most advanced products and services on the market to save you time, energy, and money.

Have a question? Add a comment below for us, and we’ll reply as soon as we can to get you on the right track!

This blog was originally posted by Jason Hugo and Anna Hartenbach at QRFS.com/blog on October 26, 2017. If this article helped you select the right escutcheon, check us out at Facebook.com/QuickResponseFireSupply or on Twitter @QuickResponseFS.

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