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Flap Valves

Introduction

Performance
Where It
Matters

Industry Leading Performance and Value

Flap Valves Intro

Fernco Flap Valves provide passive backflow protection for stormwater outfalls and drainage systems. Corrosion-resistant HMWPE and spec-friendly sizing help simplify selection and support long-term performance in harsh environments.

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Compatability

Size Range
4"-24"

Covering common stormwater outfall sizes with spec-friendly sizing for easy selection and submittals.

  • 4"
  • 6"
  • 8"
  • 10"
  • 12"
  • 15"
  • 18"
  • 24"
Flap Valves Wall Mounted

Wall Mount

Flap Valves Spiget Mount

Spigot Mount

Compatability

Wall Mount &
Spigot Mount

Choose the configuration that matches the site. Wall mount fastens to a structure. Spigot mount connects using a Strong Back shielded coupling sized to pipe OD. Confirming pipe OD and ID helps ensure proper fit.

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Specifications

Corrosion-Resistant
HMWPE Construction

Lightweight HMWPE construction supports long-term performance in harsh environments where corrosion can be a concern.

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Resources

Standards &
Spec Alignment

Built to support engineered drainage applications with published drawings and documentation for review, submittals, and spec packages.

Infrastructure

Applications

Community, Municipal, and Coastal.

flap valves applications flooding

Community Flooding

When rivers, lakes, or retention ponds rise, stormwater outfalls become an entry point for backflow. Flap Valves close automatically to keep communities dry.

flap valves applications municipal

MUNICIPAL DISCHARGE

Passive, maintenance-free backflow protection at discharge points — keeping municipal stormwater systems flowing in the right direction.

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COASTAL & TIDAL

Built from corrosion-resistant HMWPE, Fernco Flap Valves seal against tidal backpressure and coastal surge in the harshest marine environments.

Selection Support

Get the right
Flap Valve
for your project.

Share a few project details and Fernco will provide selection support and technical information for the right configuration — size, mounting style, and site conditions.

Opens a short form — takes about 3 minutes

Videos

Installation & Overview

Step-by-step installation guides and a quick look at what Fernco Flap Valves can do.

Resources

Documents & Downloads

Cut sheets, installation instructions, drawings, and more.

Resources

Flap Valve
Specifications

Part Number, Nominal Pipe Size, and Descriptions.

Effective Date: June 09, 2026 | Version 1.0 | U.S. Distribution

HMWPE Wall Mount Flap Valves

Part Number Nominal Pipe Size, in. Description (Mounting Hardware Not Included)
FV4 4 4" HMWPE Wall Mounted Flap Valve
FV6 6 6" HMWPE Wall Mounted Flap Valve
FV8 8 8" HMWPE Wall Mounted Flap Valve
FV10 10 10" HMWPE Wall Mounted Flap Valve
FV12 12 12" HMWPE Wall Mounted Flap Valve
FV14* 14 14" HMWPE Wall Mounted Flap Valve
FV15* 15 15" HMWPE Wall Mounted Flap Valve
FV16* 16 16" HMWPE Wall Mounted Flap Valve
FV18* 18 18" HMWPE Wall Mounted Flap Valve
FV20* 20 20" HMWPE Wall Mounted Flap Valve
FV21* 21 21" HMWPE Wall Mounted Flap Valve
FV24* 24 24" HMWPE Wall Mounted Flap Valve

*Special Order: Lead time and minimum quantities may apply—confirm at time of order.

Mounting Hardware Wall Mount Flap Valves

Part Number Nominal Pipe Size, in. Description
FVMS-01-US FV4, FV6, FV8 Flap Valve Mounting Set A4 S/S 4xM8 (4, 5, 6, and 8 inch)
FVMS-02-US FV10, FV12 Flap Valve Mounting Set A4 S/S 5xM8 (10 and 12 inch)
FVMS-03-US FV14, FV15, FV16 Flap Valve Mounting Set A4 S/S 6xM8 (14, 15, 16 inch)
FVMS-04-US FV18, FV20, FV21 Flap Valve Mounting Set A4 S/S 8xM8 (18, 20, 21 inch)
FVMS-06-US FV24 Flap Valve Mounting Set A4 S/S 14xM12 (24 inch)

*Special Order: Lead time and minimum quantities may apply—confirm at time of order.

MWPE Spigot Mount Flap Valves

Part Number Nominal Pipe Size, in. Description
FVS4 4 4" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS), Ductile, Plastic C900 and C905 (DIPS)
FVS6 6 6" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS), Ductile, Plastic C900 and C905 (DIPS)
FVS8 8 8" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS), Ductile, Plastic C900 and C905 (DIPS)
FVS10 10 10" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS), Ductile, Plastic C900 and C905 (DIPS)
FVS12 12 12" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS), Ductile, Plastic C900 and C905 (DIPS)
FVS14-1* 14 14" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS)
FVS14-2* 14 14" HMWPE Spigot Mounted Flap Valve for Ductile, Plastic C900 and C905 (DIPS)
FVS15* 15 15" HMWPE Spigot Mounted Flap Valve for SDR35, SDR26… Sewer Pipe (D3034)
FVS16-1* 16 16" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS)
FVS16-2* 16 16" HMWPE Spigot Mounted Flap Valve for Ductile, Plastic C900 and C905 (DIPS)
FVS18-1* 18 18" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS)
FVS18-2* 18 18" HMWPE Spigot Mounted Flap Valve for Ductile, Plastic C900, C905 (DIPS) and Large Diameter Plastic Sewer Pipe F679
FVS20-1* 20 20" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS)
FVS20-2* 20 20" HMWPE Spigot Mounted Flap Valve for Ductile, Plastic C900 and C905 (DIPS)
FVS21* 21 21" HMWPE Spigot Mounted Flap Valve for Large Diameter Plastic Sewer Pipe F679
FVS24* 24 24" HMWPE Spigot Mounted Flap Valve for Plastic SCH40, 80, 120 and Steel (IPS), Ductile, Plastic C900 and C905 (DIPS) and Large Diameter Plastic Sewer Pipe F679

*Special Order: Lead time and minimum quantities may apply—confirm at time of order.

Spigot Mount: Specify Required Coupling

Spigot mount flap valves are sold separately from the Fernco Strong Back RC shielded coupling required to complete the installation and provide a rigid, shear-resistant connection at the pipe end. Coupling selection is based on the pipe’s outside diameter (OD), with pipe material used for confirmation. Select sizes 14" and larger are offered in separate versions to accommodate the OD differences between iron pipe (IPS) and ductile iron pipe (DIPS). When contacting Fernco, reference the individual cut sheets and provide pipe OD, ID, and material so the correct valve and coupling configuration can be specified for purchase through distribution.