Bk Mueller 521-002 Black Iron Cross Fitting 3/8 in Threaded

Product Description

The BK MUELLER 521-002 is a black malleable iron cross fitting designed for threaded pipe systems operating at up to 300 psi. It features a four-way cross configuration with female iron pipe (FIP) threaded connections on all ports and a Class 150 pressure rating. The black finish is standard for gas and air distribution piping. Licensed plumbers, pipefitters, and HVAC technicians install this fitting in low- to medium-pressure piping systems where a four-way branch connection is required. At 3/8 inch, it fits compact distribution runs where space and flow demand align.

This cross fitting is used in residential and light commercial piping installations, including gas distribution, compressed air lines, and water supply systems where malleable iron construction and threaded connections are specified. The 3/8 inch size suits branch lines and secondary runs rather than main supply headers. Its Class 150 rating and 300 psi pressure capacity make it suitable for standard service conditions encountered in typical trade work.

Key Features

• Four-way cross configuration with FIP threaded connections on all ports
• Malleable iron construction for strength and impact resistance in threaded fittings
• Black finish standard for gas and air piping applications
• Class 150 rated at 300 psi for reliable service in standard-pressure systems
• 3/8 inch fitting size fits secondary branch runs in compact piping layouts

Compatibility

Designed as an OEM-style replacement or new-installation fitting for 3/8 inch FIP threaded malleable iron piping systems rated at Class 150 service.

Installation Notes

Installation is performed by a licensed plumber or pipefitter in accordance with applicable local codes and the International Fuel Gas Code (IFGC) or International Plumbing Code (IPC) as required by the service type. Shut off and depressurize the piping system fully before disassembling or installing any threaded fitting. Apply an appropriate thread sealant or PTFE tape to male threads before assembly. Do not over-tighten threaded connections, as malleable iron fittings can crack if excessive force is applied.