5/16" High Pressure Compression Union

When you’re running fuel, hydraulic, or brake circuits that can’t afford even a single drip, this 5/16″ high-pressure compression union delivers factory-grade sealing in minutes—no flaring, soldering, or specialty tools. Machined from nickel-plated brass for corrosion resistance up to 1,000 hours salt-spray, it joins two 5/16-inch hard lines and holds tight at pressures beyond 3,000 psi—well above DOT brake-system specs.

Built for brute pressure, built to last

3-piece compression design—ferrules cold-form around steel, copper, or copper-nickel tubing for a gas-tight seal.

Black-oxide plated body—resists road salt, ethanol blends, and most hydraulic fluids.

True high-pressure rating—lab-tested to 3,000 psi+; safe for power-steering, diesel, and brake systems.

Quick install—just square-cut the tube, deburr, slide on nut/ferrule, and tighten to spec.

DOT & SAE compliant—meets FMVSS 106 burst and brake impulse standards when installed on annealed tubing.

Where it works

Fuel hard lines • Hydro-boost brake setups • Power-steering return & pressure lines • Off-road air-locker plumbing • Industrial hydraulic equipment up to 3 kpsi.

How to install (2 min.)

1. Cut both tube ends square and deburr inside/outside.

2. Slide compression nut and ferrule onto the tube.

3. Insert tube fully into union body; finger-tighten nut.

4. Wrench an additional 1 ¼ turns—or follow torque chart printed on the bag.

5. Pressure-test to verify leak-free seal.

Pro tip: Use a drop of light oil on the compression threads to achieve full clamp load with less torque.