Rubber-Flex Duckbill Check Valves - RF-DBO-SB Sloped Bottom | Cla-Val

Cla-Val RF-DBO-SB Sloped Bottom Slip-On Duckbill Check Valve

The RF-DBO-SB is an elastomeric duckbill-type check valve designed for slip-on installation over existing pipe ends. The sloped bottom variant is specified where the pipe invert is positioned low within a chamber, outfall, or manhole, and full drainage without sump volume is required.

Operation

Forward differential pressure opens the elastomer lips. In backpressure or reverse flow, the lips compress to restrict return flow. The design contains no hinges, shafts, seats, or actuators. Standard opening pressure is 1–2 inches water column. Passive operation is achieved solely by pressure differential.

Applications

• Stormwater and wastewater outfalls
• Manholes with limited clearance below pipe invert
• Sewage pump stations
• Tidal, flood, or backflow protection
• Lines conveying sludge, solids, or suspended matter

Dimensions and Materials

Available in sizes 3"–72" (80–1800 mm). Slip-on construction fits over the pipe OD and is secured with heavy-duty stainless steel clamps. Elastomer options include Neoprene, EPDM, and NSF/ANSI 61 certified compounds upon request. Media compatibility must be verified for each application.

Installation Notes

For horizontal installation, the duckbill opening is oriented vertically with the sloped base at the 6 o’clock position. Up to 35° rotation is permitted for floor clearance. For DN ≤ 10", T-bolt or worm gear clamps are used; larger diameters require custom stainless steel clamps.

RF-DBO-SB vs RF-DBO

The RF-DBO is a symmetric slip-on check valve for standard pipe ends. The RF-DBO-SB features an offset bottom geometry for complete drainage in low invert or space-constrained installations.

FAQ

Is an actuator required?
No. Operation is passive, based on differential pressure.

What data is required for selection?
Pipe OD, flow rate, line pressure, backpressure, available space, and elastomer compatibility with the process fluid.