Rubber Duckbill & Inline Non-Return Valves for Drainage Backflow Prevention

One piece of reinforced rubber — no hinge to seize, no power, no maintenance schedule. Check-Flex® valves flex open under forward flow and close on backflow, stopping sewer surcharge, tidal ingress, floodwater and odours.

Inline Check
Valves

Cut-away blue pipe with black flexible liner, dark water gushing out, showing internal clamp.

Duckbill Check Valves

Black Check-Flex valve with dimensions.

Designing with Rubber Valves

Valves in stock
2,500+
50-1200mm
Inline Valves
18-900mm
Duckbill Valves
18-3000mm
Build To Order BTO

Inline Check Valves

Duckbill Check Valves

Designing with Rubber Valves

A black pipe emerges from a concrete structure, secured by metal bands, discharging onto a gabion rock mattress.

Inline Non-Return Valves: Seals Directly to the Pipe Bore

The valve sits inside the pipe and seals against the bore with an expanding clamp.

In new design that removes the headwall, the chamber structure and any preparation for angled pipes — the valve recesses fully, so nothing protrudes and no wave protection is needed.

On existing pipework it fits without modification to the pipe or the wall opening, sealing against worn, rough-cut or out-of-round bores.

50–1200mm from stock. To 3000mm built to order.

Discover Inline Check Valves
A black pipe emerges from a concrete structure, secured by metal bands, discharging onto a gabion rock mattress.

Duckbill Check Valves for Outfalls and Headwalls

The valve fits on the end of a pipe or on a headwall — flanged, wall-mounted or slide-direct.

It replaces failing flap valves with no hinge to seize and no frame to corrode, clears a low invert where headwall apron levels are tight, and self-clears in sand and shingle.

The valve keeps working while submerged, which suits tidal outfalls and CSO/ESO duty.

DN18–DN900 from stock. To DN2400 built to order.

Discover Duckbill Valves
Traceable, High-Quality Materials
Valves are constructed using traceable materials. EN 681-1:1996 — Types WC and WG Chloroprene (Neoprene) and EN 1.4404 (316L) stainless steel.

Fully Defined Elastomer Properties per ASTM D2000
The ASTM D2000 classification system provides a complete description of the elastomeric material properties. The Check-Flex® material specification is strictly controlled for key properties, including hardness, modulus, heat, ozone, and UV resistance, oil resistance, and compression set.

Standard and Optional Elastomer Materials
The standard elastomer used is Chloroprene (Neoprene). This material is highly valued for its exceptional weathering resistance, durability, and flexibility. In sewer applications, Chloroprene remains unaffected by H₂S and other common contaminants. For high-risk environments, such as industrial plants and fuel oil bunds, alternative materials can be used for valve construction. (e.g. EPDM, Nitrile and VITON)

Integrated and Controlled Manufacturing Process
The manufacturing process, from calendering to vulcanization, is integrated, which guarantees consistent production and adherence to individual valve design specifications.

ISO 9001 Certified Quality Management
The manufacturer holds an ISO9001 Certificate, accredited by IAF to National Standards, which covers the design, development, and production of rubber check valves.
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Independently Verified Hydraulic Performance
Critical hydraulic performance metrics, specifically exit velocity and headloss, are independently verified at the Utah Water Research Laboratory

Rigorous Backpressure and Valve Opening Testing
Backpressure and valve opening characteristics are subject to rigorous in-house testing

Integrated Design and Manufacturing Facility
Check-Flex® valves are designed and manufactured in Korea by an integrated specialist facility. This facility manages the entire production process, from calendering to vulcanization, which ensures consistent manufacturing within the design specifications of each individual valve.

Corrosion-Resistant Metal Components
The standard metal is 316L Stainless Steel EN 1.4404, with Super Duplex grades available for enhanced corrosion resistance in marine environments.

Cost-Efficient Injection-Moulded Valve Production
The G5-RESI, G5M, and G3M small moulded valves are manufactured using injection moulding, resulting in lower production costs, refer to specific valve model information.