Coupling, Slip x Slip PVC Schedule 40 4" x 1-1/2" (429-419)

The 429-419 is a 4" x 1-1/2" Schedule 40 PVC Reducing Coupling with Slip x Slip connections. This fitting joins two different pipe sizes inline — one socket accepts 4" PVC pipe and the opposite socket accepts 1-1/2" PVC pipe, both solvent cemented for a permanent, pressure-rated bond. The reduction from 4" to 1-1/2" is accomplished in a single fitting body, eliminating the need for a standard full-size coupling plus a separate reducer or bushing to achieve the same size transition in the pipe run.

The 4" to 1-1/2" size step is a significant two-and-a-half increment reduction — among the more aggressive inline reductions available in the Schedule 40 reducing coupling category. At this size differential, the 429-419 is not a fitting for transitioning between two pipe runs of similar capacity. It is a purpose-specific reduction fitting for applications where a large-diameter supply or collection main must transition abruptly to a much smaller downstream pipe — equipment inlets sized well below the supply main, branch connections off oversized headers, drainage collection points where a large-diameter collection line feeds a smaller-diameter discharge, and similar configurations where the upstream and downstream pipe sizes are intentionally and significantly mismatched.

Both sockets are slip connections accepting solvent cement — the 4" socket on the large side and the 1-1/2" socket on the small side — making the entire assembly a fully cemented, permanent, solvent-welded reduction with no threads involved. Proper solvent cementing practice applies to both ends: primer should be applied to the pipe end and socket interior on both sides before cement application, with the pipe inserted fully to socket depth and held in alignment through the set period. At 4", the large-side socket requires particular attention to full primer and cement coverage given the larger surface area of the joint.

Manufactured in white Schedule 40 PVC, the 429-419 provides solid corrosion resistance across a broad range of fluids, good impact performance under normal service conditions, and a substantially lower installed weight versus metal reducing couplings of equivalent size — a meaningful handling advantage in the field when working with 4" pipe. While Schedule 40 carries a lower pressure rating than Schedule 80 at equivalent sizes, it remains the appropriate specification for the majority of commercial, irrigation, and light industrial applications where system pressures fall within its rated range and the cost and weight advantages of Schedule 40 are the governing specification factors.

Specifications:

⚠️ Note: In a reducing fitting, the smaller end governs the pressure rating. The significant size differential between the 4" and 1-1/2" sockets means the two ends of this fitting are visually distinct — confirm correct pipe size insertion on each end before cementing. Use primer on both sockets and both pipe ends before cement application; do not skip priming on the 4" socket. Once cemented, neither end can be disassembled without cutting pipe.

Industries & Applications:

• Irrigation & Agricultural Systems — Transitions a 4" PVC supply main down to a 1-1/2" pipe run at a distribution point, equipment inlet, or zone connection where the supply header is significantly oversized relative to the downstream circuit it feeds and a direct inline reduction is the most compact solution
• Water & Wastewater Treatment — Used at points in treatment plant piping where a 4" collection or distribution main must transition to a 1-1/2" downstream pipe serving a sub-circuit, equipment connection, or smaller-flow branch that does not warrant a full-size continuation of the main
• Industrial Process Piping — Reduces a 4" process line inline to a 1-1/2" pipe run at equipment inlets, pump suction connections, and process sub-circuits where the upstream pipe is oversized relative to the equipment or downstream system it supplies
• Commercial Plumbing & Mechanical Systems — Applied in commercial building utility piping where a 4" service main must be reduced inline to a 1-1/2" branch or equipment connection, consolidating the reduction into a single fitting rather than a multi-component bushing and coupling assembly
• Pump Station & Equipment Connections — Installed where a 4" suction or discharge header transitions to a 1-1/2" equipment port or secondary pipe run, with the reducing coupling providing the size transition directly at the connection point in a single cemented fitting
• Swimming Pool & Aquatic Facilities — Used in pool equipment pad plumbing where large-diameter supply or return lines transition to smaller-diameter equipment connections on filters, heaters, or chemical feeders specified with 1-1/2" pipe connections