Compression fitting

A compression fitting is a type of pipe or tube fitting that seals the joint by compressing a soft metal ring (called a ferrule or olive) between the fitting body and a tightening nut. No soldering, threading, or special tools are required — just a wrench.

How it works

A compression fitting has three parts: the fitting body (which has a conical seat), the ferrule (a soft metal ring), and the nut. The tube is inserted into the fitting body, the ferrule is placed over the tube, and the nut is tightened. As the nut advances, it pushes the ferrule into the conical seat, compressing it against the tube. The ferrule deforms and seals against both the tube and the fitting body, creating a leak-tight joint.

Common applications

• Plastic water tubing: Supply lines to faucets, ice makers, and water filters.
• Copper tubing: Small-diameter copper lines in plumbing and refrigeration.
• Hydraulic and pneumatic lines: High-pressure fluid connections in machinery and automotive brake systems.
• Instrumentation: Precision tubing in laboratory and industrial instruments.

Advantages

• No heat, flux, or solder required — safe for use near flammable materials.
• Reusable — the joint can be disassembled and reassembled.
• Quick to install — a wrench and a tube cutter are the only tools needed.

Limitations

• Not suitable for very high pressures or temperatures (compared to welded or brazed joints).
• The ferrule is a one-time deformation — each assembly cycle slightly changes its shape.
• Requires clean, burr-free tube ends for a reliable seal.