B K Mueller 521-320HC Black Reducing Coupling 3/8x1/8

Product Description

The B K Mueller Industries 521-320HC is a black reducing coupling designed for threaded pipe assemblies in plumbing and gas piping applications. This fitting transitions between a 3/8-inch connection and a 1/8-inch connection, making it a practical solution wherever a pipe size reduction is required in the line. Sold in a package of 30 units, the 521-320HC is suited for professional plumbers and pipefitters who need reliable, code-appropriate fittings in quantity. The black finish is typical of malleable iron or black steel fittings used in gas distribution and low-pressure fluid piping systems.

This reducing coupling is used in residential and light commercial piping installations where a threaded reduction from 3/8 inch to 1/8 inch is needed. Common applications include gas supply lines, compressed air systems, and general plumbing rough-in work. The 30-count package quantity makes it well suited for contractors managing multiple connection points on a single job or stocking a service vehicle for recurring work.

Key Features

• Reduces from 3/8-inch to 1/8-inch threaded connections in a single fitting
• Black finish typical of malleable iron or black steel pipe fittings used in gas and fluid piping
• Package quantity of 30 units per order for contractor-volume use
• Threaded design for standard NPT assembly without special tooling
• Compact form factor for use in tight or congested piping runs

Compatibility

Designed as an OEM-style replacement or standard-use fitting compatible with 3/8-inch and 1/8-inch NPT threaded pipe systems in gas distribution, compressed air, and general plumbing applications.

Installation Notes

Installation should be performed by a licensed plumber or pipefitter in accordance with applicable local codes, including the International Plumbing Code (IPC) and International Fuel Gas Code (IFGC) where gas piping is involved. Shut off the gas or fluid supply and depressurize the line before making or breaking any threaded connections. Apply appropriate thread sealant or tape rated for the service medium before threading the fitting into place. Do not overtighten threaded fittings, as this can crack or distort the fitting body.