Bk 521-803BG Malleable Black Iron Pipe Plug 1/2 in

Product Description

The BK 521-803BG is a 1/2-inch malleable black iron pipe plug used to seal threaded pipe openings in low-pressure piping systems. Manufactured from malleable black iron meeting ANSI/ASTM A-197 material standards, this plug is suited for gas, air, water, and general plumbing applications where a secure, durable pipe closure is required. Each fitting is individually flag tagged and 100% inspected and quality tested before leaving the facility. The Mueller logo is cast directly into the body of each fitting. Threads conform to ANSI B1.20.1 for consistent fit with standard NPT pipe fittings. Dimensions comply with ANSI/ASME B16.14 and B16.39.

This plug is used in residential and light commercial plumbing, HVAC, and gas piping installations where an open threaded port must be capped off. Common applications include sealing unused branch tees, plugging test ports after pressure testing, and closing off threaded outlets on gas manifolds, boiler piping, and similar systems. The 1/2-inch size is one of the most common plug sizes encountered in field service and rough-in work.

Key Features

• Malleable black iron construction meeting ANSI/ASTM A-197 material specification
• Threads conform to ANSI B1.20.1 NPT standard for leak-free engagement
• Dimensions per ANSI/ASME B16.14 and B16.39
• Individually flag tagged and 100% inspected
• Mueller logo cast into body for quality traceability

Compatibility

Designed as a standard 1/2-inch NPT malleable iron pipe plug for use with black iron threaded pipe fittings in gas, air, and water piping systems.

Installation Notes

Installation is performed by licensed plumbers or gas fitters following applicable IFGC and IPC code requirements. Shut off and depressurize the pipe system before installing or removing any threaded plug. Apply an appropriate thread sealant or PTFE tape to the male threads before installation. Do not overtighten; use a pipe wrench and tighten to snug engagement to avoid cracking the fitting or distorting the thread.

Technical Specifications

• Size: 1/2 inch
• Material: Malleable Black Iron
• Material Standard: ANSI/ASTM A-197
• Thread Standard: ANSI B1.20.1 NPT
• Dimension Standard: ANSI/ASME B16.14, B16.39
• Weight: 0.084 pounds
• Unit of Measure: Each

Standard Information

• Brand: BK
• Manufacturer Part Number: 521-803BG