Plug, MPT PVC Schedule 80 3/8" (850-003)

This 3/8" Schedule 80 PVC Threaded Plug (MPT) provides a clean, pressure-rated closure for any standard 3/8" female NPT-threaded port, fitting outlet, or equipment connection in industrial, chemical, and commercial piping systems. Constructed in dark gray Schedule 80 PVC, it delivers the elevated wall thickness and pressure capacity required in demanding installations where standard Schedule 40 fittings are insufficient and where a reliable, corrosion-resistant threaded closure is needed at small-diameter female-threaded ports.

The male pipe thread (MPT) exterior is cut to NPT tapered thread standards, threading directly into any 3/8" female NPT port — including tee branch outlets, cross ports, coupling ends, valve bodies, manifold ports, and equipment connections — to form a pressure-tight mechanical closure when made up with thread sealant or PTFE tape. As a terminal fitting, the MPT plug is the standard solution for permanently or temporarily closing unused female-threaded ports, sealing system test points between pressure tests, blocking spare outlets on manifolds and distribution headers, and capping female-threaded connections during phased system construction or expansion. The MPT plug should not be confused with the FPT cap (848 series), which threads over a male pipe end, or the spigot plug (849 series), which cements into a socket hub — the MPT plug threads into a female port, making it the correct closure for any assembly that presents an open FPT connection requiring sealing.

Rated to approximately 920 psi at 73°F, this plug is well-suited for demanding pressure service across a broad range of industrial, chemical, and commercial fluid handling applications. Its PVC composition provides excellent resistance to acids, bases, salts, and chlorinated water, making it a durable long-term closure in corrosive environments where metal plugs would degrade, seize in the threads, or contaminate the system fluid. NSF/ANSI 61 listing confirms suitability for potable water contact, including use in drinking water distribution and treatment systems.

Install using a quality pipe thread sealant or PTFE tape on the MPT threads before engagement. Avoid over-torquing — PVC threads require hand-tight plus one to two turns; excessive force can crack the plug body or damage the receiving female threads. If used as a temporary closure during system testing or phased construction, inspect the plug and threads before reinstalling or returning the system to service. Derate pressure ratings for elevated temperatures per published derating curves.

Specifications:

Industries & Applications:

• Industrial Process Piping — Closes unused female-threaded branch outlets, spare manifold ports, and dead-end instrument taps on Schedule 80 chemical processing, water treatment, and manufacturing piping assemblies during construction, system expansion, or pressure testing phases where small-diameter threaded closures are required at high-pressure service points
• Commercial Plumbing — Caps unused 3/8" female-threaded ports on valves, manifold bodies, and fitting assemblies in high-pressure or exposed pressurized water supply systems, allowing future tap additions without cutting into the surrounding assembly
• Chemical Handling — Provides a corrosion-resistant threaded closure for unused female ports on Schedule 80 chemical distribution manifolds, metering pump assemblies, and injection line headers conveying acids, caustics, fertilizer solutions, and other fluids incompatible with metal plugs that may corrode, seize, or contaminate the system
• Irrigation & Water Distribution — Seals unused female-threaded outlets on filter housings, manifold bodies, and valve assemblies in high-pressure agricultural and municipal irrigation systems where Schedule 80 pressure ratings are specified and unused ports require a reliable threaded closure
• Water Treatment & Aquaculture — Used to close spare instrument ports, unused sampling taps, and open female-threaded connections on recirculating system headers, dosing manifolds, and treatment equipment assemblies where NSF/ANSI 61 compliance and Schedule 80 chemical resistance are required at 3/8" threaded ports
• HVAC & Mechanical Systems — Caps unused female-threaded ports on Schedule 80 cooling tower chemical feed lines, chilled water instrument manifolds, and chemically treated water system assemblies requiring elevated pressure ratings at small-diameter threaded closure points