Parker 398PSS-6-4 Shutoff Pipe Coupler Compression X Mnpt

Product Description

The PARKER 398PSS-6-4 is a single end shutoff pipe coupler designed to connect compression tubing to a male NPT threaded port in fluid and gas distribution systems. Constructed from 316 stainless steel, it delivers strong corrosion resistance in demanding service environments. The fitting accepts a 1/4-18 NPT thread on the male pipe side and uses a compression-style connection on the tube end, allowing a secure, leak-resistant joint without soldering or welding. With a maximum working pressure rating of 150 psi, this coupler suits low- to medium-pressure instrumentation, pneumatic, and process piping applications. Plumbers, pipefitters, and industrial maintenance technicians typically install this type of fitting.

This coupler is suited for residential and commercial plumbing, HVAC instrumentation lines, pneumatic control circuits, and light industrial process piping where a shutoff function is needed at a single connection point. The compression end accommodates standard tubing and the MNPT end threads directly into compatible pipe fittings, valves, or manifold ports. It is well matched to applications where 316 stainless steel is specified for corrosion resistance against moisture, mild chemicals, or outdoor exposure.

Key Features

• 316 stainless steel construction provides corrosion resistance in wet and chemically active environments
• Single end shutoff design isolates flow at the coupling point for controlled disconnection
• Compression x MNPT end connections eliminate the need for soldering or welding during installation
• 1/4-18 NPT thread size suits standard pipe fittings and manifold ports
• Rated to 150 psi maximum working pressure for low- to medium-pressure service
• Compact and lightweight at 0.15 pounds for use in tight or restricted installations

Compatibility

Designed as an OEM-style replacement or direct-install compression-to-MNPT shutoff coupler for standard 1/4-18 NPT threaded ports in plumbing, pneumatic, and instrumentation piping systems.

Installation Notes

Installation should be performed by a licensed plumber or qualified pipefitter in accordance with applicable codes such as the IPC or applicable pneumatic system standards. Shut off and depressurize the line completely before removing or installing any compression fitting. Hand-tighten the compression nut first, then use a wrench to achieve a snug, leak-free connection without overtightening, which can deform the compression ferrule. Apply appropriate thread sealant or PTFE tape to the MNPT threads before assembly.