Bk 521-802BG Malleable Black Iron Pipe Plug 3/8 in

Product Description

The BK 521-802BG is a 3/8-inch malleable black iron pipe plug designed to seal threaded pipe openings in gas, water, and general plumbing systems. Manufactured from black malleable iron meeting ANSI/ASTM A-197 material standards, this plug provides a durable, pressure-rated closure for pipe ends and unused outlet ports. Threads conform to ANSI B1.20.1 for reliable engagement with standard NPT fittings. Dimensions meet ANSI/ASME B16.14 and B16.39 specifications. Each fitting is 100 percent inspected and quality tested before shipment. Plumbers, pipefitters, and HVAC technicians reach for this plug when capping low-pressure gas lines, water distribution branches, or hydronic heating circuits.

This plug is suited for residential and light commercial plumbing and HVAC piping applications where a threaded pipe end must be sealed. Common install scenarios include capping unused tee or cross outlets, plugging test ports after pressure checks, and sealing branch lines during system modifications. The 3/8-inch size covers one of the most frequent small-diameter fitting needs in both new construction and service work. Each fitting is individually flag tagged for identification, and the Mueller logo is cast into the body.

Key Features

• Black malleable iron construction meets ANSI/ASTM A-197 material specification
• Threads conform to ANSI B1.20.1 for standard NPT compatibility
• Dimensions meet ANSI/ASME B16.14 and B16.39 standards
• 100 percent inspected and quality tested
• Individually flag tagged for easy identification on the job
• Mueller logo cast into fitting body for brand verification

Compatibility

Designed as an OEM-style replacement or new-installation fitting for standard 3/8-inch NPT threaded pipe systems in plumbing, HVAC, and general piping applications.

Installation Notes

Installation is performed by licensed plumbers or pipefitters following applicable local codes and IFGC or IPC requirements depending on the service. Depressurize and isolate the line before threading the plug into the fitting to avoid injury. Use appropriate pipe thread sealant or PTFE tape on the threads as required by the system fluid and code. Do not overtighten malleable iron fittings, as excessive force can crack the casting.

Technical Specifications

• Material: Malleable Black Iron
• Material Standard: ANSI/ASTM A-197
• Dimension Standards: ANSI/ASME B16.14, B16.39
• Thread Standard: ANSI B1.20.1
• Thread Size: 3/8 inch NPT
• Weight: 0.022 pounds
• Sold As: Each

Standard Information

• Brand: BK
• Manufacturer Part Number: 521-802BG