Butt fusion (more formally called butt fusion welding) is a method of joining two pieces of thermoplastic pipe by heating their ends and pressing them together.

It’s commonly used for pipes made from materials such as:

• High-Density Polyethylene (HDPE)
  Polypropylene (PP)

How it works

1. The ends of two pipes are aligned in a fusion machine.
2. The pipe ends are trimmed (faced) to create smooth, square surfaces.
3. A heated plate is placed between the pipe ends to melt the material.
4. The heater is removed.
5. The softened pipe ends are pressed together under controlled pressure.
6. The joint is held in place while it cools.

As the molten plastic from both pipes mixes and solidifies, it forms a continuous joint that can be as strong as—or sometimes stronger than—the original pipe.

Advantages

• Creates a leak-free joint.
• No adhesives, solvents, or mechanical fittings are required.
• High strength and durability.
• Suitable for water, gas, industrial, and wastewater pipelines.

Common applications

• Municipal water distribution systems
• Natural gas pipelines
• Mining and industrial piping
• Irrigation systems

What the finished joint looks like

A properly fused joint typically has a raised bead of plastic around the circumference where the two pipe ends were pressed together. Inspectors often examine this bead to help verify that the fusion process was performed correctly.