HDPE Flap Valves for Flood Prevention & Drainage

HDPE Flap Valves from Fernco provide a high strength, low cost solution, preventing backflow through drain or sewerage pipes.

A full range of high-quality standard and bespoke flap valves are available, ready to protect environments, homes, and properties against rising water levels.

Our Flap Valve Range includes:

Wall Mounted Flap Valve

Spigot Mounted Flap Valve

Tidal Flange Mounted Flap Valve

Tidal Wall Mounted Flap Valve

Custom Flap Valve

  • A proven flood and back water prevention method

  • Made from HMWPE 500 (a high strength HDPE specification), this offers higher impact strength, better resistance to abrasion and wear and improved UV resistance than lower grades of HDPE

  • Unique Co-extrusion seal design ensures ease and consistency of installation, with no need for additional sealants or tapes to be installed on site

  • HMWPE 500 provides improved chemical resistance to concentrated acids and alkalis compared to HDPE300

  • Manufactured above class 4 & 5 standard of DIN 19569-4 and BS7775

  • Marine grade 316 stainless steel as standard

  • Up to 60 year life expectancy with regular inspection and appropriate maintenance

    +44 (0) 1226 340 222

    sales@fernco.co.uk

    Flap Valve Standard Range

    Fernco’s Flap Valve range is designed to suit a wide variety of installation scenarios, pipe types, and site conditions. Available in multiple mounting configurations — including wall, spigot, flange, tidal and custom options — each valve is engineered for durability and performance, ease of installation, and long-term backflow prevention.

    Explore the full range below to find the best solution for your application.

    A Wall Mounted Flap Valve is a passive non-return valve designed to prevent backflow in drainage systems, particularly in environments prone to variable water levels such as rivers, estuaries, and flood-prone areas.

    These valves are affixed directly to a flat wall surface, typically at the end of an outfall pipe, with their hinges positioned at the top (12 o’clock) to allow the flap to open under minimal forward flow and close securely when flow reverses.

    Fernco’s Wall Mounted Flap Valves are constructed from high-molecular-weight polyethylene (HMWPE 500) and marine grade 316 stainless steel, providing a strong yet lightweight structure that is corrosion and chemical resistant, providing superior UV stability and impact resistance.

    The Integrated EPDM seals ensure superior performance up to 7mWc without the need for additional sealants to be applied on site, ensuring consistence performance on every installation.

    Available from sizes ranging from DN100 to DN1000 Fernco’s Wall Mounted Flap Valves are built to exceed standards such as DIN 19569-4 and BS7775, offering long service life with minimal maintenance.

    Product CodeDNA
    (mm)    		B
    (mm)    		C
    (mm)    		D
    (mm)    		E
    (mm)    		F
    (mm)    		G
    (mm)    		Mounting Hole PCD
    (mm)    		Pressure
    (mwc)    		Weight
    (kg)
    FV100100212235771291062075618371
    FV125125254268771421272336522572
    FV150150274291791541372486224072
    FV200200341349791791702987131273
    FV225225351367791911763226331573
    FV250250379392792021903466535073
    FV300300429442792282143966540074
    FV350350499517792682494727446076
    FV400400544565792932725227251577
    FV450450594615793182975727256578
    FV50050064966799*34332462275620710
    FV60060075477099*39337772177725714
    FV7007008951080**134*632**44896198850737
    FV8008009951180**134*682**498106198950744
    FV90090010951280**134*732**5481161981050752
    FV1000100011951380**134*782**5981261981150760
    FV1100110014101592**128***886**70514501551330785
    FV1200120015101692**128***936**75515501551430795
    FV1300130016101792**128***986**805165015515307106
    FV1400140017101892**128***1036**855175015516307116
    FV1500150018101992**128***1086**905185015517307128

    * Dimension taken from the back of the wall plate to front plate strengthening ribs.
    ** These values are taken from the top of the lifting bracket.
    *** Dimension taken from the back of the wall plate to the front edge of lifting eye.

    Mounting Sets

    Flap ValveMounting HolesPart CodeDescription
    FV100 - 2004FVMS-01Flap Valve Mounting Set A4 Stainless Steel Bolts and Chemical Anchors 4xM8
    FV225 - 3005FVMS-02Flap Valve Mounting Set A4 Stainless Steel Bolts and Chemical Anchors 5xM8
    FV350 - 4506FVMS-03Flap Valve Mounting Set A4 Stainless Steel Bolts and Chemical Anchors 6xM8
    FV500 - 6008FVMS-04Flap Valve Mounting Set A4 Stainless Steel Bolts and Chemical Anchors 8xM8
    FV700 - 100014FVMS-06Flap Valve Mounting Set A4 Stainless Steel Bolts and Chemical Anchors 14xM12
    FV1100 - 130024FVMS-08Flap Valve Mounting Set A4 Stainless Steel Bolts and Chemical Anchors 24xM12
    FV1400 - 150028FVMS-09Flap Valve Mounting Set A4 Stainless Steel Bolts and Chemical Anchors 28xM12

    Larger sizes available on request

    • 1. Offer the Flap Valve to the wall in the desired fixing position, ensuring the hinges are at 12 o’clock.
    • 2. Mark the drill positions where the wall mounting holes are present and use a spirit level to make sure the Flap Valve is straight.
    • 3. Remove the Flap Valve and drill holes where marked using a suitable drill. Use the correct size drill bit as indicated in the table below. Ensure the hole depth is consistent with the requirements indicated in the table below.
    • 4. Dust and debris must be cleaned from all drilled holes and the wall surface.
    • 5. Insert the chemical capsules into the hole.
    • 6. Using a suitable drill, drill the bolts provided into the holes and chemical capsules, until the depth of the hole has been reached.
    • 7. Detach the drill from the bolt and remove excess residue from around the hole. Leave the chemical to cure, curing time is indicated in the table below.
    • 8/9. Offer the Flap Valve over the bolts, tighten on the supplied washers and nuts to the recommended torque as given in the table below.

    A Spigot Mounted Flap Valve is a passive non-return tidal valve designed to be connected directly to the end of a drainage pipe, providing reliable backflow prevention in systems exposed to surface water, stormwater, or tidal influence.

    Fernco’s Spigot Mounted Flap Valves are constructed from high-molecular-weight polyethylene (HMWPE 500) and marine grade 316 stainless steel, providing a strong yet lightweight structure that is corrosion and chemical resistant, providing superior UV stability and impact resistance.

    These valves are installed either by using our Fernco shear-banded coupling for enhanced stability and flow performance or by inserting the spigot into the pipe with an EPDM sealing tape for an internal compression fit.

    The flap opens under minimal forward flow and seals automatically under reverse pressure. The Integrated EPDM seals ensure superior performance up to 7mWc. Connect with a Fernco Shear-banded coupling to ensure consistent performance on every installation.

    The Fernco Flange mounted range is manufactured with a 10° Valve inclination, giving suitability in tidal applications, turbulent flow or to counter any connecting pipework gradient

    Available in sizes ranging from DN100 to DN630, Fernco’s Spigot Mounted Flap Valves are built to exceed standards such as DIN 19569-4 and BS7775, offering dependable protection with straightforward installation and minimal maintenance.

    Product CodeDNSpigot OD (mm)Spigot ID (mm)A (mm)B (mm)C (mm)D (mm)E (mm)Pressure (mwc)Weight (kg)
    FVS100100908321223512526423472
    FVS11011011010221223512526723472
    FVS12512512511525426813026726072.7
    FVS15015014012325426813027126072.9
    FVS16016016014827429113527927473.1
    FVS20020018015927429113527727473.5
    FVS22522520018434034914428432774.6
    FVS25025022521135126714628835074.8
    FVS28028025023537939215029337475.6
    FVS30030028026337939215129637675.6
    FVS35035031530042944215730042576.8
    FVS400400355333499517167309490710.3
    FVS450450400375544565173307543712.7
    FVS500500450422594615178369597714.7
    FVS525525500469649667195*378*648717.8
    FVS600600560526685698199*393*673720
    FVS630630630591754770224*405*748725.5

    * Dimension taken from end of spigot to front plate strengthening ribs.

    Spigot mounted Flap Valves can be connected to a pipe in two ways:

    1. By using a Fernco Shear banded coupling to connect the spigot flap valve to the connecting pipe, this method will offer superior stability of the valve. The valve can be sized specific to the connecting pipe’s outside diameter and therefore remove the need to seal inside the pipeline and restrict bore.
    2. By inserting the spigot inside of the pipe and securing into position using a supplied EPDM sealing tape. For this option simply select the spigot size (column Spigot ID) which will fit inside the pipe.

    Please ensure supplied OD and ID measurements are accurate so the correct bush can be specified with the Spigot Flap Valve.

    Installation Guide: Spigot Mounted Flap Valve using Shear Banded Coupling

    • 1. Ensure the pipe has a straight/flat end face.
    • 2. Clean the outer pipe surface leaving a smooth surface for the coupling to seal onto.
    • 3. Measure the coupling width, mark half this measurement on both the flap valve spigot and connecting pipe.
    • 4. If using a bush slide the bush onto the Flap Valve spigot until the edge of the bush and the marked line are flush.
    • 5. Slide the coupling over the bush until the end faces are flush, hand tighten the end clamp. If no bush is required slide the coupling onto the spigot until the edge of the coupling and marked line are flush, hand tighten the end clamp.
    • 6. Butt the Flap Valve spigot up to the main pipe, the coupling should now be in-line with the line previously marked on the pipe. Ensure the Flap Valve is in the correct orientation (hinge mechanism at 12 o’clock), hand tighten the end clamp.
    • 7. Tighten all clamp bands to the recommended torque (see coupling label) in sequence across the width of the coupling starting with the central shear band.

    Installation Guide: Spigot Mounted Flap Valve using Sealing Tape

    • 1. Ensure the pipe end has a straight/flat surface for mounting.
    • 2. Clean away any debris from the internal surface of the pipe.
    • 3. Take the Sealing tape supplied with the Flap Valve, peel away the self-adhesive backing and wrap around the external surface of the Flap Valve spigot.
    • 4. Ensure the outside diameter of the tape is now approximately 5mm larger than the internal diameter of the pipe to ensure a compressive fit.
    • 5. Insert the spigot section of the Flap Valve into the pipe until the pipe end is flush with the Flap Valves back plate. When inserting ensure the Flap Valve hinge mechanism is at 12 o’clock.
    Sealing Tape Sizes
    Finished ProductPart CodeDescriptionQuantity (Metres)
    EPDM Sealing StripFVSMS-01EPDM Spigot Sealing Strip For Flap Valve Spigots DN100, DN125, DN1502.5m
    EPDM Sealing StripFVSMS-02EPDM Spigot Sealing Strip For Flap Valve Spigots DN200, DN225, DN2505m
    EPDM Sealing StripFVSMS-03EPDM Spigot Sealing Strip For Flap Valve Spigots DN300, DN350, DN4007.5m
    EPDM Sealing StripFVSMS-04EPDM Spigot Sealing Strip For Flap Valve Spigots DN450, DN500, DN60010m

    A Flange Mounted Flap Valve is a passive non-return tidal valve designed to be connected directly to the end of a drainage pipe, providing reliable backflow prevention in systems exposed to surface water, stormwater, or tidal influence..

    Fernco’s Spigot Mounted Flap Valves are constructed from high-molecular-weight polyethylene (HMWPE 500) and marine grade 316 stainless steel, providing a strong yet lightweight structure that is corrosion and chemical resistant, providing superior UV stability and impact resistance.

    These valves are secured to standard pipe flanges using industry-recognised drilling patterns such as BS4504, ISO 7005 (DIN), AS2129, and AS4087, ensuring compatibility across a wide range of infrastructure systems.

    The flap opens under minimal forward flow and seals automatically under reverse pressure. The Integrated EPDM seals ensure superior performance up to 7mWc. Connect with a Fernco Shear-banded coupling to ensure consistent performance on every installation.

    The Fernco Flange mounted range is manufactured with a 10° Valve inclination, giving suitability in tidal applications, turbulent flow or to counter any connecting pipework gradient

    Available in sizes ranging from DN100 to DN600, Fernco’s Flange Mounted Flap Valves are built to exceed standards such as DIN 19569-4 and BS7775, offering dependable protection with straightforward installation and minimal maintenance.

    Pipe DNFlange OptionsDescription
    Flange
    DN100FVTF100-1DN100 BS4504 / ISO 7005 (DIN) PN10/PN16
    FVTF100-2DN100 AS2129 Table C/D AS4087 PN14/PN16
    DN125FVTF125-1DN125 BS4504 / ISO 7005 (DIN) PN10/PN16
    FVTF125-2DN125 AS2129 Table C/D/E AS4087 PN14/PN16
    DN150FVTF150-1DN150 BS4504 / ISO 7005 (DIN) PN10/PN16
    FVTF150-2DN150 AS2129 Table C/D AS4087 PN14/PN16
    DN200FVTF200-1DN200 BS4504 / ISO 7005 (DIN) PN10
    FVTF200-2DN200 BS4504 / ISO 7005 (DIN) PN16
    FVTF200-3DN200 AS2129 Table C/D AS4087 PN14/PN16
    DN250FVTF250-1DN250 BS4504 / ISO 7005 (DIN) PN10
    FVTF250-2DN250 BS4504 / ISO 7005 (DIN) PN16
    FVTF250-3DN250 AS2129 Table C/D AS4087 PN14/PN16
    DN300FVTF300-1DN300 BS4504 / ISO 7005 (DIN) PN10
    FVTF300-2DN300 BS4504 / ISO 7005 (DIN) PN16
    FVTF300-3DN300 AS2129 Table C/D/E AS4087 PN14/PN16
    DN350FVTF350-1DN350 BS4504 / ISO 7005 (DIN) PN10
    FVTF350-2DN350 BS4504 / ISO 7005 (DIN) PN16
    FVTF350-3DN350 AS2129 Table C/D/E
    DN400FVTF400-1DN400 BS4504 / ISO 7005 (DIN) PN10
    FVTF400-2DN400 BS4504 / ISO 7005 (DIN) PN16
    FVTF400-3DN400 AS2129 Table C/D/E AS4087 PN14/PN16
    DN450FVTF450-1DN450 BS4504 / ISO 7005 (DIN) PN10
    FVTF450-2DN450 AS2129 Table C/D/E AS4087 PN14/PN16
    FVTF450-3DN450 AS2129 Table C/D/E AS4087 PN14/PN16
    DN500FVTF500-1DN500 BS4504 / ISO 7005 (DIN) PN10
    FVTF500-2DN500 BS4504 / ISO 7005 (DIN) PN16
    FVTF500-3DN500 AS2129 Table C/D/E
    DN600FVTF600-1DN600 BS4504 / ISO 7005 (DIN) PN10
    FVTF600-2DN600 BS4504 / ISO 7005 (DIN) PN16
    FVTF600-3DN600 AS2129 Table C/D AS4087 PN14/PN16

    Product drawings available for approval at quoting stage.

    Other flange adaptors can be manufactured on request.

    • 1. Attach the Tidal Flange Mounted Flap Valve to the desired flange, ensuring that the hinges of the flap valve are level.
    • 2. Tighten the fixings as per the flange specification, the flange fixing kit is not provided.

    A Tidal Mounted Flap Valve is a passive non-return tidal valve designed to be connected directly to the end of a drainage pipe, providing reliable backflow prevention in systems exposed to surface water, stormwater, or tidal influence.

    The Tidal Valve’s construction incorporates a 10-degree inclination, ensuring continuous even compression of the seal, even when submerged or under conditions of turbulent back pressure. This maintains the flap door in a naturally closed and seated position, unaffected by external hydraulic fluctuations. Consequently, the valve delivers consistent operational performance, effectively preventing reverse flow and preserving optimal system performance.

    Fernco’s Spigot Mounted Flap Valves are constructed from high-molecular-weight polyethylene (HMWPE 500) and marine grade 316 stainless steel, providing a strong yet lightweight structure that is corrosion and chemical resistant, providing superior UV stability and impact resistance.

    Available in sizes ranging from DN100 to DN600, Fernco’s Tidal Wall Mounted Flap Valves are built to exceed standards such as DIN 19569-4 and BS7775, offering dependable protection with straightforward installation and minimal maintenance.

    Product CodeDNA (mm)B (mm)C (mm)D (mm)E (mm)F (mm)Mounting Hole PCD (mm)Pressure (mwc)Weight (kg)
    FVT10010021223526721210237618372.6
    FVT15015027429127926014841922173.8
    FVT20020035126728834021149328376.3
    FVT22522537939228837023551731176.8
    FVT25025037939229638526352133376.8
    FVT30030042944230045030056738378.5
    FVT400400544565367595422788523717.2
    FVT500500685698393*695526868628723.6
    FVT600600754770405*780591930705728.8

    * Dimension taken from the back of the wall plate to front plate rib.

    Mounting Sets

    Tidal Wall Mounted Flap ValveMounting HolesSizePart Code
    FVT1004M8M8 FVMS-01
    FVT1505M8M8 FVMS-02
    FVT2005M8M8 FVMS-02
    FVT2255M8M8 FVMS-02
    FVT2506M8M8 FVMS-03
    FVT3006M8M8 FVMS-03
    FVT4008M8M8 FVMS-04
    FVT50010M8M8 FVMS-05
    FVT60010M8M8 FVMS-05
    • 1. Offer the Flap Valve to the wall in the desired fixing position, ensuring the top fixing bolt is at 12 o’clock.
    • 2. Mark on the wall the drill positions where the wall mounting holes are present.
    • 3. Remove the Flap Valve and drill holes where marked using a suitable drill and the correct size drill bit as shown in the table below. Ensure the hole depth for all holes is consistent as shown in the table below.
    • 4. Dust and debris must be cleaned from all drilled holes and the wall surface.
    • 5. Insert the chemical capsules into the hole.
    • 6. Using a suitable drill, drill the bolts provided into the holes and chemical capsules, until the depth of the hole has been reached.
    • 7. Detach the drill from the bolt and remove excess residue from around the hole. Leave the chemical to cure, curing time is shown in the table below.
    • 8. Offer the Flap Valve over the bolts, tighten on the supplied washers and nuts to the recommended torque as shown in the table below.

    Wall Mounting Kit Installation Requirements

    Bolt SizeDrill Bit RequiredDrilled DepthRecommended Tightening Torque
    M810mm80mm4Nm

    Chemical Capsule Cure Time

    Temp °CCure Time
    -15 – -1030 h
    -9 – -516 h
    -4 – 010 h
    +1 – +545 min
    +6 – +1030 min
    +11 – +2020 min
    +21– +305 min
    +31 – +403 min

    The Fernco HDPE Flap Valve is a one-way passive non-return valve engineered to prevent backflow from endangering commercial and residential drainage.

    Installed at the discharge end of pipelines or culverts, it allows water to exit freely while automatically closing against reverse pressure, safeguarding the upstream system from flooding or contamination.

    Manufactured from High-Molecular Weight Polyethylene (HMWPE / PE500), the Fernco Flap Valve range delivers exceptional durability and reliability, even in the harshest marine environments. The HMWPE construction makes the Flap Valves lightweight for ease of handling and installation yet robust enough to withstand the demands of tidal forces, submersion, and flood-prone environments. Compared to cast iron alternatives, the Fernco Flap Valves offer a significant reduction in opening pressure, minimising the volume of stagnant water retained behind the gate while providing excellent long-term corrosion resistance.

    The product range includes configurations for wall, spigot, tidal, and flange mounting options, ensuring that they can be installed in every environment. The Flap Valves use a patented sealing technology that performs under both low and high pressures while eliminating the variance in installation quality. An integrated EPDM sponge seal ensures a watertight seal between the mounting surface and valve, removing the need for any additional sealing materials.

    Built to Perform

    • High-strength HDPE for long-term durability

    • Rigid, impact-resistant construction

    • Operates from -30°C to 130°C

    • Manufactured to DIN 19569-4 compliance

    • Low cracking head for fast valve response

    Engineered for Water Environments

    • Ideal for tidal, submerged, and marine use

    • Low moisture absorption

    • Chemically resistant to acids, bases & solvents

    • Non-toxic and safe for water systems

    • UV-stable for outdoor exposure

    Easy to Install & Sustain

    • Lightweight for faster, safer installation

    • No grout needed between frame and wall

    • Fully recyclable, HDPE and 316 stainless steel

    • No scrap value — theft deterrent

    • Minimal maintenance required

    • Available in bespoke configurations

    Wall MountedSpigot MountedTidal Flange MountedTidal Wall MountedCustom Mounting Options
    FV100FVS100/FVS110FVTF100FVT100
    FV125FVS110/FVS125FVTF125-
    FV150FVS150/FVS160FVTF150FVT150
    FV200FVS200/FVS225FVTF200FVT200
    FV225FVS225-FVT225
    FV250FVS250/FVS280FVTF250FVT250
    FV300FVS280/FVS300FVTF300FVT300
    FV350FVS350FVTF350-
    FV400FVS400FVTF400FVT400
    FV450FVS450FVTF450-
    FV500FVS500FVTF500FVT500
    FV600FVS600/FVS630FVTF600FVT600
    FV700---
    FV800---
    FV900---
    FV1000---

    Need help with installation? Watch the videos below for clear, step-by-step guidance on how to correctly install Fernco’s Wall Mounted and Spigot Mounted Flap Valves. Whether you’re on-site or planning ahead, these quick tutorials walk you through the process and highlight key tips for a secure, trouble-free fit.

    Browse the gallery below to see Fernco’s Flap Valves across the full range of mounting options, including wall mounted, spigot mounted, tidal, and flange variants. These images showcase the design, construction, and installation of each valve type, helping you visualise how they function in real-world applications.

    Looking for detailed specifications and technical information? Download the Fernco Flap Valves data sheet below for a complete overview of product dimensions, materials, installation guidance, and performance characteristics — all in one convenient PDF.

    To download the data sheet, simply click the button below and fill in the short form — it only takes a few seconds and gives you instant access to all the information required for specifying or installing our flap valves with confidence.

    Need the full technical specification?

    The complete product guide for engineers and installers.

    Our datasheet includes everything you need to specify, install, or compare Fernco Flap Valves — from dimensions and pressure ratings to materials, mounting options, and performance standards. It’s the go-to reference for engineers, contractors, and consultants working in drainage, flood defence, or water infrastructure.

    To access the download, just fill in the quick form provided. It only takes a moment and gives you instant access to the full PDF. Once submitted, you’ll be able to view, save, or share the datasheet whenever you need it.

    Frequently Asked Questions

    A flap valve is a type of non-return valve designed to allow water to flow out of a pipe or structure while preventing backflow. It works by using a hinged flap that opens under forward flow and closes automatically when water tries to reverse direction. Fernco’s Flap Valves use a top-mounted hinge and integrated seals to ensure reliable operation across a range of flow conditions.

    Fernco Flap Valves are used in drainage, stormwater, flood protection, and wastewater systems — especially where pipes discharge into rivers, estuaries, coastal zones, or areas prone to high water levels. They’re commonly installed at the end of outfall pipes, culverts, chambers, or tanks, and are available in wall, spigot, flange, and tidal-mounted options to suit different site requirements.

    The standard range covers pipe sizes from DN100-DN1500, with flange compatibility across common standards like BS4504, ISO 7005 (DIN), and AS2129. Larger or custom sizes may be available on request, and spigot valves can be matched precisely to pipe outer diameters using bushes or couplings for a secure fit.

    All Fernco Flap Valves are manufactured from high-density polyethylene (HDPE) for strength, impact resistance, and long-term durability. They include 316 stainless steel components for corrosion resistance, and EPDM co-extruded seals to ensure watertight performance. The valves are UV-stable, chemically inert, and suitable for submerged or harsh environments, with a life expectancy of up to 60 years under proper maintenance.

    Installation depends on the mounting type. Wall-mounted and tidal wall valves are fixed directly to a flat surface using chemical anchors and stainless steel bolts. Spigot-mounted valves can be inserted into the pipe with sealing tape or attached using Fernco couplings. Flange-mounted options bolt directly to standard pipe flanges. All mounting kits and installation instructions are available from Fernco, and many valves can be installed without grout or specialist tools.

    Got a question or need help choosing the right product for your project?

    Whether you’re looking for technical advice, sizing guidance, or bespoke configurations, our team is here to help.

    Simply fill out the quick enquiry form and one of our product specialists will get back to you as soon as possible.