Bk Mueller 521-374HN Black Reducing Coupling 1-1/2x3/4 in

Product Description

The BK MUELLER 521-374HN is a black malleable iron reducing coupling designed for threaded pipe installations. It connects a 1-1/2 inch line to a 3/4 inch line using female iron pipe (FIP) threads on both ends. Rated at Class 150 with a liquid and gas pressure rating of 300 psi, this fitting handles both gas and liquid service in demanding trade applications. The black finish is standard for gas distribution and low-pressure steam systems. Plumbers and pipefitters install this fitting when reducing pipe size in a run without additional adapters.

This reducing coupling is suited for residential and light commercial piping systems where a threaded iron fitting is required. Common applications include natural gas supply lines, compressed air distribution, and hydronic heating systems. The FIP thread standard on both ends allows direct makeup onto male-threaded pipe or nipples. It is a single-piece unit requiring no separate bushings or inserts to achieve the reduction from 1-1/2 inches to 3/4 inches.

Key Features

• Malleable iron construction rated for 300 psi liquid and gas service
• Class 150 classification for standard threaded iron pipe systems
• Female iron pipe (FIP) threads on both ends for direct pipe makeup
• Reduces 1-1/2 inch to 3/4 inch in a single fitting - no bushing required
• Black finish standard for gas and low-pressure steam applications

Compatibility

Designed as an OEM-style replacement or new-installation fitting for Class 150 threaded malleable iron piping systems using FIP connections.

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 depressurize the line completely before disassembling any threaded connections. Apply an approved pipe thread sealant or PTFE tape to male threads before makeup. Do not overtighten - use a pipe wrench with a backup wrench on the adjacent fitting to avoid stressing adjacent joints.