Southland 521-320HC Black Iron Reducing Coupling 3/8x1/8

Product Description

The SOUTHLAND 521-320HC is a malleable black iron reducing coupling designed for joining pipes of two different diameters in threaded piping systems. It transitions from a 3/8-inch female thread to a 1/8-inch female thread, making it a standard component in gas, air, and low-pressure fluid distribution lines. Each fitting is individually flag tagged and carries the Mueller logo cast directly into the body. The 521-320HC meets ANSI/ASTM A-197 material standards and ANSI/ASME B16.3 and B16.39 dimensional standards, with threads conforming to ANSI B1.20.1. Licensed plumbers and pipefitters are the typical installers in both residential and light commercial settings.

This reducing coupling is suited for residential and light commercial piping applications where a threaded reduction between 3/8-inch and 1/8-inch pipe is required. Common uses include natural gas distribution, compressed air lines, and low-pressure steam or water systems. The black iron finish makes it appropriate for gas service where galvanized fittings are not permitted. The fitting is sold individually and is well suited for service work, repairs, and new installations requiring a reliable threaded reduction.

Key Features

• Malleable black iron construction per ANSI/ASTM A-197
• Dimensions conform to ANSI/ASME B16.3, B16.14, and B16.39
• NPT threads per ANSI B1.20.1 for reliable, leak-resistant connections
• Individually flag tagged for easy identification on the job
• Mueller logo cast into fitting body — confirms manufacturer traceability
• 100% inspected and quality tested before shipment

Compatibility

Designed as an OEM-style replacement or new-installation fitting for threaded black iron piping systems using 3/8-inch to 1/8-inch NPT connections in gas, air, or low-pressure fluid service.

Installation Notes

Installation should be performed by a licensed plumber or pipefitter in accordance with applicable local codes and IFGC or IPC requirements. Shut off and verify zero pressure in the line before disassembling or installing any threaded fitting. Apply an appropriate thread sealant or PTFE tape rated for the service medium before making up the joint. Do not over-tighten; hand-snug plus wrench turns per standard practice is sufficient to achieve a pressure-tight seal on NPT threads.

Technical Specifications

• Material: Malleable Black Iron
• Material Standard: ANSI/ASTM A-197
• Dimensional Standard: ANSI/ASME B16.3, B16.14, B16.39
• Thread Standard: ANSI B1.20.1 (NPT)
• Inlet Size: 3/8 inches female NPT
• Outlet Size: 1/8 inches female NPT
• Weight: 0.108 pounds
• Sold As: Each

Standard Information

• Brand: SOUTHLAND
• Manufacturer Part Number: 521-320HC