Bk 521-804BG Malleable Black Iron Pipe Plug 3/4 in

Product Description

The BK 521-804BG is a 3/4-inch malleable black iron pipe plug designed to close off threaded pipe ends in plumbing, HVAC, and gas distribution systems. Cast from black malleable iron meeting ANSI/ASTM A-197 material standards, this plug delivers reliable thread engagement and a secure seal in both low-pressure and standard-pressure applications. The Mueller logo is cast directly into the body. Each fitting is individually flag tagged and has been 100% inspected and quality tested before shipment. At 0.138 pounds, it is a compact, heavy-duty fitting suited for professional installation.

This plug is used to cap off threaded openings in residential and light commercial piping systems, including gas lines, water supply lines, and hydronic heating systems. It is a common part of rough-in work, pressure testing setups, and service repairs where a threaded port needs to be sealed. Plumbers, pipefitters, and HVAC technicians regularly stock this fitting for both new construction and maintenance work.

Key Features

• Black malleable iron construction per ANSI/ASTM A-197 for durability in standard pipe applications
• Dimensions conform to ANSI/ASME B16.3, B16.14, and B16.39 standards
• Threads cut to ANSI B1.20.1 NPT specification for consistent fitment
• Mueller logo cast into body for brand identification and quality assurance
• Individually flag tagged for easy identification at the job site
• 100% inspected and quality tested at the factory

Compatibility

Designed as an OEM-style replacement or new-installation fitting for 3/4-inch NPT threaded pipe systems in plumbing, HVAC, and gas piping applications.

Installation Notes

Installation is performed by licensed plumbers or pipefitters following applicable IPC and IFGC code requirements. Shut off and depressurize the pipe system completely before installing or removing any threaded fitting. Apply appropriate thread sealant or PTFE tape to the male threads before hand-tightening, then wrench-tighten to achieve a leak-free connection. Do not overtighten malleable iron fittings, as the material can crack under excessive torque.

Technical Specifications

• Material: Malleable Black Iron
• Material Standard: ANSI/ASTM A-197
• Pipe Size: 3/4 inch
• Thread Standard: ANSI B1.20.1 NPT
• Dimension Standards: ANSI/ASME B16.3, B16.14, B16.39
• Weight: 0.138 pounds
• Unit of Measure: Each

Standard Information

• Brand: BK
• Manufacturer Part Number: 521-804BG