Bushing, MPT x FPT (Flush Style) PVC Schedule 80 3/8" x 1/4" (839-052)

This 3/8" × 1/4" Schedule 80 PVC Flush Bushing provides a compact, all-threaded size reduction from a 3/8" female-threaded port down to a 1/4" female NPT threaded outlet, purpose-built for small-bore instrumentation runs, gauge port connections, and fine-bore control system piping in Schedule 80 PVC pressure systems. The 3/8" MPT exterior threads directly into any compatible 3/8" FPT port — on an instrument manifold, gauge isolation valve, small-bore tee branch, or equipment nozzle — while the 1/4" FPT interior receives any compatible 1/4" male-threaded gauge, transducer, thermowell, pressure switch, or instrument fitting on the reduced side.

The 3/8" × 1/4" size combination defines a highly specific application niche within the 839-series. Both pipe sizes are small-bore by any standard — 3/8" NPT appears at instrument supply lines, gauge isolation valve ports, instrument manifold connections, and fine-bore chemical dosing branches, while 1/4" NPT is the near-universal standard connection size for pressure gauges, pressure transducers, thermowells, pressure switches, and virtually all small-bore industrial instrumentation. The 839-052 bridges these two instrumentation-scale pipe sizes in a single fitting, reducing a 3/8" threaded port directly to the 1/4" gauge-port standard without intermediate adapters or additional fittings in the assembly.

In instrument supply and control system piping, where fitting count, assembly length, and potential leak point minimization are design priorities, the ability to accomplish a 3/8"-to-1/4" reduction in a single compact flush bushing is a meaningful practical advantage. Instrument runs are often routed through congested control panels, instrument racks, and equipment cabinets where every added fitting and joint represents both a potential leak source and a spatial encumbrance. The flush style of the 839-052 reinforces this compactness advantage — the absence of a protruding hex shoulder allows the bushing to sit fully inside the receiving 3/8" FPT port, presenting only the 1/4" outlet face rather than extending axially into the limited clearance space at the instrument connection point.

As with all 839-series fittings, the all-threaded MPT × FPT configuration distinguishes this bushing from socket-end alternatives. The 839 MPT end threads into female-threaded ports — making it the correct selection wherever the receiving fitting presents a 3/8" FPT opening. No solvent cement, primer, or curing time is required at the bushing installation point; both the installation into the 3/8" port and the downstream 1/4" instrument connection are made up with PTFE tape and thread sealant in a fully threaded assembly. This is particularly practical in instrument and control system applications where field installation speed, clean workmanship, and the ability to disassemble and reassemble connections during calibration and maintenance intervals are operational requirements.

Manufactured in dark gray Schedule 80 PVC, this bushing delivers the wall thickness and mechanical strength suited to industrial, chemical, and commercial pressure service in small-bore instrumentation and process control piping. PVC's broad chemical resistance covers acids, bases, salts, chlorine, and most common process fluids, providing long service life in corrosive environments where metal bushings would corrode, pit, or contaminate instrument calibration results through metallic ion introduction into the measured fluid stream. NSF/ANSI 61 listing confirms suitability for potable water contact.

Rated to approximately 1300 psi at 73°F — reflecting the significantly elevated pressure ratings of Schedule 80 PVC fittings at small bore sizes — this bushing is well suited for the full range of instrument supply pressures encountered in commercial and industrial Schedule 80 PVC systems. At 3/8" and 1/4" NPT, both the inlet and outlet threads are particularly susceptible to over-torque damage given their small thread engagement area. Apply two to three wraps of PTFE tape to the 3/8" MPT exterior before threading into the receiving port — hand-tighten plus one to two turns only, using a small open-end wrench on the bushing body rather than pipe wrenches, which risk over-torquing at this small thread size. Apply PTFE tape to all male threads engaging the 1/4" FPT outlet; gauge and instrument body connections at 1/4" NPT should be hand-tight plus one turn only. Apply published pressure derating factors for service temperatures above 73°F.

Specifications:

Industries & Applications:

• Instrumentation & Gauge Port Connections — Reduces a 3/8" FPT port at an instrument manifold, gauge isolation valve, or small-bore tee branch to the 1/4" NPT standard connection size for pressure gauges, pressure transducers, thermowells, pressure switches, and other small-bore instrumentation in industrial and commercial PVC pressure systems — the defining application for the 3/8" × 1/4" size combination across all system types
• Industrial Process Piping — Provides a compact all-threaded size reduction at 3/8" FPT instrument tap positions on Schedule 80 PVC process headers, chemical distribution lines, pump manifolds, and equipment supply connections in chemical processing, water treatment, and manufacturing facilities where downstream instrumentation presents 1/4" NPT inlets
• Chemical Dosing & Injection Systems — Installs at 3/8" FPT ports on chemical dosing manifolds, injection quill assemblies, and reagent distribution headers where 1/4" NPT pressure monitoring instrumentation, flow-indicating devices, or back-pressure regulators must be connected in small-bore chemical handling systems handling acids, caustics, and aggressive process fluids
• Water & Wastewater Treatment — Reduces 3/8" FPT instrument connection ports to 1/4" NPT gauge and transducer connections on Schedule 80 PVC process headers, chemical feed manifolds, filter vessel instrument taps, and pump station monitoring points in municipal and industrial water treatment facilities
• Control Panel & Instrument Rack Piping — Used within control panel enclosures, instrument rack assemblies, and analyzer shelter piping where 3/8" Schedule 80 PVC instrument supply lines must be reduced to 1/4" NPT at gauge, transducer, and analyzer connection points — the flush style and compact all-threaded construction are particularly valued in space-constrained panel and rack environments
• Commercial Plumbing & Mechanical Monitoring — Provides a 1/4" NPT gauge port connection at 3/8" FPT instrument tap positions on Schedule 80 PVC water distribution headers, pump station piping, and mechanical system monitoring points in commercial building and facility management systems where pressure monitoring instrumentation is specified at small-bore tap locations
• HVAC & Mechanical Systems — Installed at 3/8" FPT instrument tap positions on Schedule 80 PVC cooling tower chemical feed lines, treated water monitoring headers, and glycol system pressure monitoring points where 1/4" NPT pressure gauges and transducers must be connected at small-bore instrument tap positions in mechanical system piping