NIBCO valves are widely used in commercial, residential, and industrial applications. Available in several configurations and material types, they are well known for their reliable construction and efficient operation.
In most hydronic and process piping systems, check valves are used to:
- Ensure forward flow
- Prevent backflow
- Protect the system equipment, such as boilers, pumps, and downstream components
NIBCO F-918-B - Overview
The model F-918-B is a non-manual swing check valve with flanged connections and durable cast-iron construction, with possible variations depending on project demand.
Material Construction/ Schema
Below is the construction material description:
- Body Bolt: Steel ASTM A307
- Identification Plate: Aluminum
- Bonnet: Cast Iron ASTM A126 Class B
- Body Gasket: Synthetic Fibers
- Body Nut: Steel ASTM A563
- Side Plug: Brass ASTM B16 Alloy C36000
- Hanger Pin: Brass ASTM B16 Alloy C36000
- Hanger: Ductile Iron ASTM A536 / Cast Bronze ASTM B584 Alloy C84400
- Disc: Ductile Iron ASTM A536 with Bronze Face Ring
- Seat Ring: Cast Bronze ASTM B584 Alloy C84400
- Disc Nut: Brass ASTM B16 Alloy C36000
- Body: Cast Iron ASTM A126 Class B
NIBCO F-918-B - Variants
Below is the description and size for each valve variation available:
- F-918-B - Flanged Swing Cast Iron Check Valve
- Available sizes: 2'', 2.1/2'', 3'', 4'', 5'', 6'', 8'', 10'', 12''
- Application: For non-critical systems, this valve relies primarily on gravity-assisted closure
- F-918-B-LW - Flanged Swing Cast Iron Check Valve with Lever and Weight
- Available sizes: 2.1/2'', 3'', 4'', 5'', 6'', 8'', 10'', 12''
- Application: For systems that need faster closure during flow reversal, the fixed weight assists closure and helps reduce slam
- F-918-B-LS - Flanged Swing Cast Iron Check Valve with Lever and Spring
- Available sizes: 2.1/2'', 3'', 4'', 5'', 6'', 8'', 10'', 12''
- Application: For systems that need more precise disc movement (spring-assisted closure for faster response and reduced slam)
Check Valves Common Failure Symptoms
Technicians often search for NIBCO check valve technical information when the system begins to operate inefficiently and, in critical cases, equipment damage or downtime occurs. Some operational issues may indicate that the valve is not working correctly. Indications such as leakage, backflow, water hammer, and pressure variation can indicate valve failure. Understanding the possible symptoms of valve failure is indispensable for finding the best field solution and resolving the problem.
Causes and Symptoms
Incomplete Valve Disc Closure
Sometimes the swing disc stays open due to debris caught between the disc and the seat or a worn hinge pin. Also, due to corrosion on the seat face, this can cause the symptoms:
- Backflow
- Dripping at downstream isolation points
- Sounds like a fully open valve
Water Hammer Damage
Swing check valves are prone to slamming shut under rapid flow reversal. The water hammer can cause:
- Cracked discs
- Accelerates wear on the hinge pin
- Bent hinge arms
Incorrect Installation Orientation
A typical installation mistake. The technician must ensure that the valve is installed in a horizontal position, with sufficient clearance distance from curves and elbows, and with proper flow direction. If the points mentioned are not respected, it will cause:
- Valve premature failure
- Disc damage
- Valve never closes properly
Disc or Seat Wear
Water turbulence inside the valve erodes sealing surfaces. The symptoms are:
- Leakage
- Poor shutoff
- Noisy operation
External Leakage
Commonly misdiagnosed as valve failure, it can have its roots in the system's external components rather than in the valve itself. Issues such as flange deterioration, uneven bolt torque, and aged gaskets can lead the system to:
- Water leaks closer to the valve
- Dripping in the connections
Diagnostic Workflow for the F-918-B
Following the best practices troubleshooting sequence, below is a coherent workflow to diagnose valve/system failure:
1 - Check the basics
- Check if the valve is installed in the correct flow direction.
- Check the system pressure and ensure the installed valve rating supports the operating conditions.
- Make sure the valve is installed horizontally, confirm the approved installation orientation for the F-918-B (typically horizontal for many swing check valves), and follow NIBCO’s instructions.
Tip: Many check valve issues are caused by installation orientation, flow direction, or system conditions—verify these first before opening the valve.
2 - Mechanical Obstructions
Older systems may be prone to debris, which can lead to valve failure. The recommended procedure to check if it's the case is to stop the water circulation, isolate, depressurize, and verify zero energy before loosening fasteners, then remove the bonnet and inspect:
- Seat face
- Hinge area
If anything blocks the disc from swinging freely, the entire valve will not be able to seal the water flow.
3 - Evaluate the Disc and Hinge Assembly
Inspect:
- Hinge pin wear
- excessive lateral movement
- Disc
Problems such as an elongated hinge pin, a damaged disc, and a distorted arm will require replacement parts, depending on the evaluation. Below is a general video showing a swing check valve hinge pin assembly removal:
Video credit: Matco-Norca
4 - System conditions
Before taking action to replace parts or the entire valve, it is essential to check whether the root of the problem lies in other system components; the valve malfunction may be a symptom, not a cause. When possible, it's recommended to check:
- Pump operation (looking for short cycles and sudden stops)
- Water flow and velocity (related to piping, valve under-/oversized)
- System pressure
When to Replace and When to Rebuild?
That's the question many technicians or facility managers struggle with: whether to rebuild or replace the faulty valve. It's a decision that must take specific considerations into account before being made.
When Rebuilding Makes Sense
Although NIBCO Check Valve doesn't offer rebuild kits for check valves, there is a list of replacement parts that can be ordered separately to repair any faulty F-918-B valve. Below is the complete spare parts list for F-918-B Check valve:
- Hanger
- Hanger Pin
- Disc
- Disc Bolt
- Disc Nut
- Bonnet
- Gasket
- Body Bolts
- Body Bolt Nuts
- Side Plug
If the damaged or faulty part is one of the items listed above, the valve can be serviced rather than replaced, which is the most cost-efficient solution. However, other factors must be considered to ensure that rebuilding is the correct choice.
- Casting is in good shape and still solid
- No heavy damage to the seat
- Hinge area is serviceable (enough clearance/maintenance space)
You can find all available NIBCO valve repair parts on our website.
When Replacement is the Better Choice
If the valve shows damage or a fault in a component not listed in the spare parts list above, the only option will be to replace the entire valve. Below are the cases that indicate direct replacement:
- Flanges are corroded or uneven
- Seat beyond repair
- The body shows cracking
- Hydraulic shock damage
You can find all available NIBCO Check Valves on our website.
How to Identify the Correct NIBCO Replacement Valve or Replacement Parts
Usually, NIBCO Inc.'s Check Valves have a nameplate on the body with all relevant information, such as part numbers, models, and pressure ratings. For old valves without clear identification, there are several ways to identify the correct valve model once it's installed and operating in the field. Below are some references needed to ensure the correct replacement valve model or parts:
- Valve Type: Identify by visual inspection and system drawings (if available), especially to confirm swing check style and any lever/weight or lever/spring variation
- Valve Size - To be measured across the flanges
- Pressure Rating- Visible on the valve body casting
- End Connections - For F-918-B = ANSI Flanged (as per first model letter indication ''F'')
When uncertain, providing photos of both sides of the valve—and the nameplate, if present—ensures accurate identification.
Liberty Supply's team confirms models/parts daily; don't hesitate to reach out for any support needed.
Installation Best Practices to Maximize F-918-B Service Life
An installation that follows the manufacturer's best practices can dramatically increase the check valve's longevity. Some guidelines to help you in your field installation are listed below:
Horizontal Installation
Ensure that the NIBCO's F-918-B is installed horizontally, as it will avoid:
- Fluttering
- Incomplete closure
- Premature disc wear
Gasket Selection
Gaskets are a significant cause of external leakage. Ensure to select your installation gaskets based on:
- Fluid type
- Fluid temperature
- System pressure
Torque Bolts
Uneven torque can be a problem for check valves. Use a calibrated torque wrench and tighten in a star pattern to the manufacturer’s recommended torque; overtightening should be avoided. Uneven torque can:
- Create future leak paths
- Warp flanges
- Distort seating surfaces
Flow Velocity
Ensure that the system is well-sized to avoid high flow velocity, which can accelerate disc impact and hinge wear.
Strainers for Debris-Prone Systems
When possible, a basket strainer to filter debris in the system can add years to a check valve's life.
NIBCO's Support Page and Technical Documentation
If you are looking for more information on the NIBCO Inc. F-918-B Check Valve, don't hesitate to reach out to us; our sales team is ready to support you.
Below are some helpful links for more information:
NIBCO Parts and Valves Available in Liberty Supply
Check the Check Valves Range Available
Liberty Supply is a customer-centric organization. We focus on hydronic and steam systems for commercial and industrial facilities. As a B2B distributor within the "needs business," our foundational pillars are knowledge, communication, and speed. Relationships are built through hard work and consistent delivery of value. No exceptions. Our team maintains that with each transaction, we start back at zero.
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- Phone: 844-448-0880
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