1/2" Hex MNPT Plug

This Harrington Process Solutions 1/2" hex MNPT plug, alternate part 3850S005, seals a 1/2" female threaded port from the male side, with a hex head that lets you drive it cleanly and securely with a wrench. Made of Schedule 80 PVC, it is a durable, corrosion-resistant choice for closing off ports in water-treatment and process plumbing where strength and reliability matter and where a lighter fitting might not provide enough margin.

Plug versus cap

While a cap covers a male pipe end, a plug threads into a female opening—making it the correct fitting for sealing unused outlets on manifolds, valve bodies, tees, and fittings. The hex head provides a solid grip for tightening and later removal, which is especially useful at test points or future-expansion ports that may need to be reopened down the road for service or system changes. Choosing a proper plug rather than improvising a seal keeps the connection clean, reliably sealed, and easy to service when the time comes.

• 1/2" hex-head plug, male NPT (MNPT)
• Schedule 80 PVC construction for strength and durability
• Threads into 1/2" female ports
• Hex head for secure wrench installation and removal
• Corrosion- and chemical-resistant
• Suited to process and higher-pressure plumbing

To install, apply PTFE thread-seal tape or a PVC-compatible thread sealant to the male threads, thread the plug in by hand to start it straight, and finish with a measured wrench turn—avoid over-tightening, which can crack PVC even on the heavier Schedule 80 body. Always confirm that the plug's pressure and temperature ratings match your system before returning it to service, and inspect the threads if you reuse the plug after removal. A reliable, easy-to-use fitting for sealing ports in filtration manifolds and process assemblies, it is also a smart spare to keep in the kit for the unexpected open port that turns up on nearly every job. Strong, serviceable, and easy to install correctly, this Schedule 80 plug is the dependable way to seal a port cleanly and reopen it later when your system changes. Keeping spares on hand means the unexpected open port never slows you down. Inexpensive and reusable, it is a practical addition to any installer's kit for the open ports that turn up on nearly every job.