4 inch x 3 inch Strong Back Shielded Reducing Coupling Connects Cast Iron, Copper, PVC, Steel or Lead Pipe

Fernco 1056-43RC 4 inch x 3 inch Flexible Coupling – For Cast Iron, Plastic & Other Pipe Materials

The Fernco 1056-43RC flexible coupling is designed for transition applications involving 4-inch and 3-inch piping systems of differing materials. Engineered for robust performance, this coupling joins cast iron, plastic (PVC or ABS), steel, copper, and lead piping with a secure, watertight seal. Commonly used in gravity-flow DWV (drain, waste, and vent) systems, it provides a dependable solution for adapting between dissimilar pipe types.

This model features corrosion-resistant stainless steel clamps and a durable elastomeric sleeve, allowing for flexibility and ease of installation in both new construction and retrofit applications. The RC (reducer coupling) designation allows for the step-down from 4-inch to 3-inch pipe diameters while maintaining system integrity across varying substrates.

Product Specifications

• Model: 1056-43RC
• Size: 4 inch x 3 inch
• Material Compatibility: Cast Iron, PVC, ABS, Steel, Copper, Lead
• Coupling Material: Flexible PVC
• Clamp Material: 300-series Stainless Steel
• Application: Non-pressure DWV systems
• Compliance: ASTM C1173, CSA B602, UPC/IAPMO listed

Performance Features

• ✅ Transition Compatibility – Designed for joining different pipe materials and sizes
• ✅ Flexible Body – Accommodates pipe movement and vibration, reducing joint stress
• ✅ Stainless Steel Bands – Torque clamps provide secure sealing at rated specifications
• ✅ Non-Pressure System Use – Ideal for DWV systems where reliable flow continuity is essential

Installation Guidance

The Fernco 1056-43RC is installed using a torque wrench calibrated to 60 in-lbs on each clamp to ensure even compression and leak resistance. No solvent welding, adhesives, or special tools are required. Installers must verify pipe end compatibility and cleanliness prior to coupling placement. Installation in underground or concealed locations should conform to applicable plumbing code provisions.

Common Applications

This coupling is routinely used in residential and commercial drain systems, particularly during pipe repair, material conversion, or remodeling where differing pipe types and sizes intersect. Its flexibility and code compliance make it an industry-standard choice for plumbing contractors.

Technical Note

This fitting is not rated for pressurized potable water lines or force mains. It is intended exclusively for gravity-driven DWV applications under standard temperature ranges. Always consult manufacturer guidance and local code when specifying for critical systems.