Inline Check Valves for Reliable Backflow Protection

The Fernco MwStop® is a non-return valve that uses an EPDM membrane to protect commercial and residential properties from backflow flooding.

The membrane prevents the return of unwanted water, odours, and pests while allowing your property to discharge as normal.

Installation is simple and flexible, with full compatibility across common pipe materials and sizes.

Engineered for durability, the Fernco MwStop® delivers a long and reliable service life with options for three different back pressure ratings to suit any system requirement.

Our MwStop® Range includes:

Fernco MwStop® –
Standard

Fernco MwStop® –
Short

Fernco MwStop® –
One Collar

Fernco MwStop® –
PE

Fernco MwStop®-
RatStop

Fernco MwStop®-
Gasket

  • Reliable backflow protection with an EPDM diaphragm that seals instantly under reverse flow

  • Pressure activated surge action that helps reduce sediment build up

  • Available in 3mWC, 5mWC and 8mWC pressure ratings to suit system requirements

  • Wide DN75 to DN1000 size range for domestic and commercial drainage systems

  • Suitable for horizontal or vertical in pipe installation

  • Corrosion resistant 316 stainless steel body with durable EPDM membrane

  • PE housing option for coupling mounted applications

  • Optional RatStop protection to prevent rodent ingress

    +44 (0) 1226 340 222

    sales@fernco.co.uk

    Fernco MwStop® Inline Check Valve Range

    Fernco’s Inline Check Valve range is designed to suit a wide variety of drainage systems, pipe materials and installation requirements. Available in Standard, Short, One Collar, PE housing and Reverse configurations, each valve is engineered for reliable backflow protection, installation flexibility and long-term performance, with additional options available for enhanced pest protection and improved sealing where required.

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

    Fernco MwStop® – Standard

    Provides reliable backflow prevention with a full-length body that fits standard pipeline layouts. It has the ability to be reversed at the installation stage to change the direction of flow/protection.

    Product Code Membrane OptionsDNOutside DiameterLength of steel bodyHost pipe inside diameter (min / max)
    CV-STD100-5545, 6510097mm220mm98 - 111mm
    CV-STD125-5545, 65125115mm255mm116 - 124mm
    CV-STD150-5545, 65150144.5mm310mm145.5 - 158.5mm
    CV-STD200-181-5545, 65200 (181)181mm400mm182 - 199mm
    CV-STD200-191-5545, 65200 (191)191mm425mm192 - 209mm
    CV-STD225-55-5545, 65225215mm470mm216 - 233mm
    CV-STD250-230-5545, 65250 (230)230mm520mm231 - 252mm
    CV-STD250-240-5545, 65250 (240)240mm520mm241 - 258mm
    CV-STD300-5545, 65300265mm600mm266 - 283mm
    CV-STD300-283-5545, 65300 (283)283mm650mm284 - 301mm
    CV-STD300-290-5545, 65300 (290)290mm650mm291 - 308mm
    CV-STD350-5545, 65350340m745mm341 - 362mm
    CV-STD400-370-5545, 65400 (370)370mm760mm371 - 392mm
    CV-STD400-390-5545, 65400 (390)390mm800mm391 - 412mm
    CV-STD450-5545, 65450443mm900mm444 - 465mm
    CV-STD500-5545, 65500490mm970mm491 - 504mm
    CV-STD600-5545, 65600587mm1200mm588 - 597mm
    CV-STD700-5545, 65700690mm1350mm691 - 708mm
    CV-STD750-5545, 65750750mm1500mm751 - 768mm
    CV-STD800-5545, 65800790mm1580mm791 - 808mm
    CV-STD900-5545, 65900885mm1780mm886 - 913mm
    CV-STD1000-5545, 651000985mm1950mm986 - 1008mm
    Reverse Option
    CV-STDR100-5545, 6510097mm220mm98 - 111mm
    CV-STDR125-5545, 65125115mm255mm116 - 124mm
    CV-STDR150-5545, 65150144.5mm310mm145.5 - 158.5mm
    CV-STDR200-181-5545, 65200 (181)181mm400mm182 - 199mm
    CV-STDR200-191-5545, 65200 (191)191mm425mm192 - 209mm
    CV-STDR225-5545, 65225215mm470mm216 - 233mm
    CV-STDR250-230-5545, 65250 (230)230mm520mm231 - 252mm
    CV-STDR250-240-5545, 65250 (240)240mm520mm241 - 258mm
    CV-STDR300-5545, 65300265mm600mm266 - 283mm
    CV-STDR300-283-5545, 65300 (283)283mm650mm284 - 301mm
    CV-STDR300-290-5545, 65300 (290)290mm650mm291 - 308mm
    CV-STDR350-5545, 65350340m745mm341 - 362mm
    CV-STDR400-370-5545, 65400 (370)370mm760mm371 - 392mm
    CV-STDR400-390-5545, 65400 (390)390mm800mm391 - 412mm
    CV-STDR450-5545, 65450443mm900mm444 - 465mm
    CV-STDR500-5545, 65500490mm970mm491 - 504mm
    CV-STDR600-5545, 65600587mm1200mm588 - 597mm
    CV-STDR700-5545, 65700690mm1350mm691 - 708mm
    CV-STDR750-5545, 65750750mm1500mm751 - 768mm
    CV-STDR800-5545, 65800790mm1580mm791 - 808mm
    CV-STDR900-5545, 65900885mm1780mm886 - 913mm
    CV-STDR1000-5545, 651000985mm1950mm986 - 1008mm

    Fernco MwStop® – Short

    A compact version of the standard valve with a reduced installation length. Ideal for tight spaces or retrofit situations where a full-size valve won’t fit. No ability to be reversed.

    Product CodeOther shore optionsDNO/dLengthPipe Size I/d (min / max)
    CV-SH100-5545, 6510097mm160mm98 - 111mm
    CV-SH125-5545, 65125115mm190mm115 - 124mm
    CV-SH150-5545, 65150144.5mm200mm143.5 - 158.5mm
    CV-SH200-181-5545, 65200 (181)181mm270mm178 - 199mm
    CV-SH200-191-5545, 65200 (191)191mm275mm188 - 209mm
    CV-SH225-5545, 65225215mm310mm212 - 233mm
    CV-SH250-230-5545, 65250 (230)230mm320mm227 - 252mm
    CV-SH250-240-5545, 65250 (240)240mm350mm237 - 258mm
    CV-SH300-5545, 65300265mm380mm260 - 283mm
    CV-SH300-283-5545, 65300 (283)283mm400mm278 - 301mm
    CV-SH300-290-5545, 65300 (290)290mm400mm285 - 308mm
    CV-SH350-5545, 65350340m500mm333 - 362mm
    CV-SH400-370-5545, 65400 (370)370mm500mm363 - 392mm
    CV-SH400-390-5545, 65400 (390)390mm500mm383 - 412mm
    CV-SH450-5545, 65450443mm550mm436 - 465mm
    CV-SH500-5545, 65500490mm600mm491 - 504mm
    CV-SH600-5545, 65600587mm800mm580 - 597mm
    CV-SH700-5545, 65700690mm870mm691 - 708mm
    CV-SH750-5545, 65750750mm979mm747 - 768mm
    CV-SH800-5545, 65800790mm1000mm787 - 808mm
    CV-SH900-5545, 65900885mm1110mm886 - 913mm
    CV-SH1000-5545, 651000985mm1475mm981 - 1008mm

    Fernco MwStop® – One Collar

    A valve featuring a single collar connection for applications where only one end requires anchoring or where a unique pipe configuration demands a simplified connection on one side.

    Product CodeOther shore optionsDNO/dLengthPipe Size I/d (min / max)
    CV-OC100-5545, 6510097mm160mm98 - 111mm
    CV-OC125-5545, 65125115mm190mm115 - 124mm
    CV-OC150-5545, 65150144.5mm200mm143.5 - 158.5mm
    CV-OC200-181-5545, 65200 (181)181mm270mm178 - 199mm
    CV-OC200-191-5545, 65200 (191)191mm275mm188 - 209mm
    CV-OC225-5545, 65225215mm310mm212 - 233mm
    CV-OC250-230-5545, 65250 (230)230mm320mm227 - 252mm
    CV-OC250-240-5545, 65250 (240)240mm350mm237 - 258mm
    CV-OC300-5545, 65300265mm380mm260 - 283mm
    CV-OC300-289-5545, 65300 (283)283mm400mm278 - 301mm
    CV-OC300-290-5545, 65300 (290)290mm400mm285 - 308mm
    CV-OC350-5545, 65350340m500mm333 - 362mm
    CV-OC400-370-5545, 65400 (370)370mm500mm363 - 392mm
    CV-OC400-390-5545, 65400 (390)390mm500mm383 - 412mm
    CV-OC450-5545, 65450443mm550mm436 - 465mm
    CV-OC500-5545, 65500490mm600mm491 - 504mm
    CV-OC600-5545, 65600587mm800mm580 - 597mm
    CV-OC700-5545, 65700690mm870mm691 - 708mm
    CV-OC750-5545, 65750750mm979mm747 - 768mm
    CV-OC800-5545, 65800790mm1000mm787 - 808mm
    CV-OC900-5545, 65900885mm1110mm886 - 913mm
    CV-OC1000-5545, 651000985mm1475mm981 - 1008mm

    Fernco MwStop® – PE

    Fernco MwStop® with plastic housing made of PE, to be mounted using flexible couplings.

    Product CodeOther shore optionsDNO/dLengthConnection
    CV-PE075-5545, 657575mm125mmConnection to pipe requires two couplings.
    CV-PE110-5545, 65110110mm210mm
    CV-PE125-5545, 65125125mm240mm
    CV-PE160-5545, 65160160mm310mm
    CV-PE200-5545, 65200200mm400mm

    Fernco MwStop® – RatStop

    Additional protection against animal and pests to protect the diaphragm from damage.

    Product CodeDNDescription
    CV-RS100100Fernco MwStop® Ratstop 316 Stainless Steel DN100
    CV-RS125125Fernco MwStop® Ratstop 316 Stainless Steel DN125
    CV-RS150150Fernco MwStop® Ratstop 316 Stainless Steel DN150
    CV-RS200-181200 (181)Fernco MwStop® Ratstop 316 Stainless Steel DN200-181
    CV-RS200-191200 (191)Fernco MwStop® Ratstop 316 Stainless Steel DN200-191
    CV-RS225225Fernco MwStop® Ratstop 316 Stainless Steel DN225
    CV-RS250-230250 (230)Fernco MwStop® Ratstop 316 Stainless Steel DN250-230
    CV-RS250-240250 (240)Fernco MwStop® Ratstop 316 Stainless Steel DN250-240
    CV-RS300-283300Fernco MwStop® Ratstop 316 Stainless Steel DN300-283
    CV-RS300-290300 (283)Fernco MwStop® Ratstop 316 Stainless Steel DN300-290

    Fernco MwStop® – Gasket

    In some cases when the check valve is not sufficient to the pipe, additional external seals may be required.

    Product CodeDNDescription
    CV-G100100Fernco MwStop® EPDM Rubber Gasket DN100
    CV-G125125Fernco MwStop® EPDM Rubber Gasket DN125
    CV-G150150Fernco MwStop® EPDM Rubber Gasket DN150
    CV-G200-181200 (181)Fernco MwStop® EPDM Rubber Gasket DN200-181
    CV-G200-191200 (191)Fernco MwStop® EPDM Rubber Gasket DN200-191
    CV-G225225Fernco MwStop® EPDM Rubber Gasket DN225
    CV-G250-230250 (230)Fernco MwStop® EPDM Rubber Gasket DN250-230
    CV-G250-240250 (240)Fernco MwStop® EPDM Rubber Gasket DN250-240
    CV-G300-283300Fernco MwStop® EPDM Rubber Gasket DN300-283
    CV-G300-290300 (283)Fernco MwStop® EPDM Rubber Gasket DN300-290

    The Fernco MwStop® check valve is designed to allow sewer or surface water to move freely in one direction, while effectively protecting properties against backwater flooding and odour.

    When subjected to increasing pressure, the integrated EPDM diaphragm will raise upwards so water can flow freely below the valve in the direction of the flow. As soon as water flows against the direction of the flow, the valve fills up to provide a tight seal to prevent any backflow flooding.

    The rising water pressure triggers controlled surge flushing, which ensures the regular removal of existing sediments. These valves will also prevent unpleasant odours in the pipe network. The Fernco MwStop can be supplied affixed with a RatStop to prevent rodents and other wildlife travelling up the drainage system and into the property.

    The Fernco MwStop® can be installed in practically any pipe, in both horizontal and vertical applications in just a few minutes. Different mounting methods enable a wide range of applications; these include bracket mounted, flange mounted, installation at the end of the pipe, or in-line with Fernco couplings.

    Engineered for Reliable Flow Control

    • Prevents reverse flow flooding in sewer and surface water systems

    • EPDM diaphragm provides tight sealing under back pressure

    • Available in 3mWC, 5mWC and 8mWC ratings

    • Pressure response creates controlled surge flushing

    Designed for Flexible Installation

    • Suitable for horizontal and vertical in pipe installation

    • Available in Standard, Short, One Collar and PE variants

    • Compatible with common pipe materials and sizes

    • Bracket, end of pipe and in line mounting options

    Built for Long Term Protection

    • 316 stainless steel body for corrosion resistance

    • Durable EPDM membrane for extended service life

    • Optional rodent barrier protects the diaphragm

    • Gasket option available for annular gap sealing

    Clamp or bracket mounting edge inside a manhole

    Installation as part of the pipe

    TypeShore A HardnessBack pressure ratingMinimum pipe gradient
    Soft Membrane453mWC1%
    Standard Membrane555mWC2%
    Hard Membrane658mWC

    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 Inline Check Valves — from membrane options and back pressure ratings to dimensions, installation configurations and ancillary components. It’s an essential reference for engineers, contractors and consultants working in sewer and surface water drainage systems.

    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

    An inline check valve is a non-return valve installed within a pipe to prevent reverse flow. The Fernco MwStop® uses an EPDM diaphragm that lifts under forward flow and seals under back pressure, preventing sewer or surface water from flowing back into the system.

    Fernco Inline Check Valves are available with three membrane hardness options providing back pressure ratings of 3mWC, 5mWC and 8mWC. This allows the valve to be selected based on system head and hydraulic requirements.

    Yes. The Fernco MwStop® is suitable for both horizontal and vertical in-pipe installation. It can be installed as part of the pipe run, bracket mounted inside a manhole or configured to suit various site conditions.

    The range covers DN75 to DN1000 depending on the configuration. Multiple body styles are available, including Standard, Short, One Collar and PE housing variants to accommodate different installation requirements.

    Yes. The valve prevents odours and unwanted backflow, and an optional stainless steel rodent barrier can be fitted to protect against pest ingress and safeguard the diaphragm.

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

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