1/8 inch Black Iron Coupling Female x Female

1/8 inch Black Malleable Iron Coupling – Threaded FPT x FPT for Pipe-to-Pipe Extensions

The 1/8 inch Black Iron Coupling is a straight-threaded pipe fitting used to join two male-threaded pipe sections of equal nominal diameter. Constructed from malleable cast iron conforming to ASTM A197, this coupling is commonly used in rigid piping systems where a secure and mechanically strong joint is required. The black finish is intended for use in non-corrosive, indoor environments such as gas distribution or low-pressure air systems.

This full-coupling features female NPT threads at both ends and is manufactured to the dimensional requirements of ASME B16.3. Its design supports use in applications where steel or iron pipe extensions are needed without the use of welding or brazing.

Key Features

• ✅ Material: Malleable cast iron (ASTM A197)
• ✅ Thread Standard: NPT (ANSI/ASME B1.20.1)
• ✅ Nominal Size: 1/8 inch FPT x FPT
• ✅ Pressure Rating: Meets ASME B16.3 specifications for threaded fittings in low- and medium-pressure applications
• ✅ Finish: Black oxide coating suitable for dry gas, steam, and air systems

Installation Guidelines

Apply thread sealant (pipe dope) or PTFE tape to male threads before assembly. Engage threads evenly to avoid misalignment and over-torquing. Use pipe wrenches on the hex surfaces or exterior of the coupling—not the thread ends—to prevent damage during installation. Couplings must be installed in systems that are properly supported and aligned to avoid joint stress.

Applications

Commonly used in natural gas and LP gas systems, compressed air piping, low-pressure steam systems, and general mechanical piping assemblies. Also suitable for use in fire protection, hydronic heating, and other systems requiring durable threaded connections between short or long pipe sections.

Code and Compliance Notes

Black iron couplings are typically not used in potable water systems unless certified for such use. They are accepted in most mechanical codes for fuel gas and air applications when installed per manufacturer instructions and local authority requirements.

The 1/8 inch Black Iron Coupling is a standard-grade fitting used for straight inline connections in rigid pipe systems where threaded mechanical joints are preferred. Its durable construction, dimensional consistency, and compatibility with industry-standard pipe threads make it a reliable choice for high-integrity applications in commercial and residential systems.