Ay Mcdonald 4423-378 Pex-a Poly Insert Coupling

Product Description

The AY MCDONALD 4423-378 is a reducing poly insert coupling designed to connect 1-inch PEX-A tubing to 3/4-inch PEX-A tubing in potable water and hydronic piping systems. The insert-style fitting slides into the PEX tubing bore and is secured with a crimp ring or clamp ring, creating a leak-resistant mechanical joint without soldering or threading. This type of fitting is installed by licensed plumbers and pipefitters during new construction, remodel, or repair work wherever a reduction in line size is required. The poly body resists corrosion and scale, making it well suited for residential and light-commercial plumbing applications.

This coupling is used in PEX-A radiant heat systems, domestic hot and cold water distribution, and manifold-fed home-run plumbing layouts. Its reducing geometry allows a plumber to step down from a 1-inch main or sub-main to a 3/4-inch branch line without adding a separate bushing or adapter. It is appropriate for concealed installations in walls, floors, and ceilings where access after completion is limited, so a reliable connection is essential on the first install.

Key Features

• Reducing insert design connects 1-inch PEX-A to 3/4-inch PEX-A in a single fitting
• Poly body construction resists corrosion, scale buildup, and chemical degradation
• Compatible with standard crimp-ring and clamp-ring installation tools
• No soldering, threading, or open flame required for installation
• Suited for potable water and hydronic closed-loop applications

Compatibility

Designed as an OEM-style insert fitting for use with 1-inch by 3/4-inch PEX-A tubing in residential and light-commercial plumbing and hydronic systems.

Installation Notes

Installation is performed by a licensed plumber in accordance with local plumbing codes and the IPC. Shut off the water supply and depressurize the line before cutting and fitting. Use a go/no-go gauge after crimping or clamping to verify the connection meets manufacturer and code requirements. Do not reuse a fitting that has been seated and crimped.

Technical Specifications

• Inlet Size: 1 inch
• Outlet Size: 3/4 inch
• Fitting Type: Reducing Insert Coupling
• Tubing Compatibility: PEX-A
• Body Material: Poly
• UPC: 813927019789

Standard Information

• Brand: AY MCDONALD
• Manufacturer Part Number: 4423-378