Pipe Fusion Series: What Is Saddle Fusion?

April 15, 2024

What Is Saddle Fusion?

Saddle fusion is a specialized form of heat fusion, a process used to join two pipes or fittings made from thermoplastic materials like polypropylene (PP)  and high-density polyethylene (HDPE). This technique involves creating a saddle-shaped connection by melting the surfaces of both the main pipe and the branch or saddle fitting. The heat applied fuses the materials together, resulting in a strong, leak-resistant joint.

Saddle Fusion Process

The key steps involved in saddle fusion are:

1. Preparation

Before starting the saddle fusion process, it’s essential to thoroughly clean and prepare the pipe and fitting surfaces. Any dirt, debris, or contaminants should be removed to ensure a clean fusion.

2. Clamping

Securely clamp the saddle fusion machine onto the pipe, then secure the saddle fitting into the machine. The clamps hold the components in place during the fusion process, ensuring they do not move or misalign.

3. Marking and Alignment

Mark the position where the saddle fitting will be attached to the main pipe. Proper alignment is crucial for a successful fusion, so take care to align the fitting accurately.

4. Heating

Use a specialized heating tool to heat the surfaces of both the main pipe and the saddle fitting. The heating tool typically includes heating plates or a heating element that is placed against the surfaces to be fused.

5. Heating Time

Allow sufficient time for the heating process. The duration will depend on factors such as the type and thickness of the thermoplastic material. It is crucial to follow the manufacturer’s guidelines for the specific materials being fused.

6. Cooling

Once the heating is complete, remove the heater and apply proper fusion force, per manufacturer’s recommendations, and allow the fused joint to cool. Cooling times can vary, and it’s important not to disturb the joint during this phase to ensure proper solidification of the melted thermoplastic material.

7. Inspection

After the joint has cooled, inspect the joint visually to ensure there are no irregularities, and that the fusion is uniform and without any visible defects. The fusion bead should have a characteristic “three-bead” shape. 

8. Testing

Conduct pressure tests or other relevant quality checks to verify the integrity of the saddle fusion joint. This step is crucial to ensure that the joint is leak-resistant and meets the required performance standards.

9. Documentation

Maintain detailed documentation of the saddle fusion process, including the fusion parameters, cooling times, and any quality control tests performed. Proper documentation is essential for quality assurance and compliance.

Saddle Fusion vs. Other Types of Pipe Fusion

Saddle fusion isn’t the only effective method of pipe fusion. See how it compares to other popular pipe fusion methods like butt fusion, socket fusion and electrofusion.

Saddle Fusion

Used to create branch connections by attaching a saddle-shaped fitting to an existing pipe. The saddle is heated, and pressure is applied to weld it to the main pipe.


  • Ideal for creating branch connections in a pipeline.
  • Requires minimal excavation, making it suitable for repairs and retrofits.
Butt Fusion

Involves joining two pipe ends by heating them to their melting point and then pressing them together. The melted material fuses, creating a seamless, end-to-end connection.


  • Produces leak-proof and long-lasting joints.
  • Suitable for a wide range of thermoplastic materials.
  • No need for additional adhesives or solvents.
  • Minimal maintenance is required.
  • Consistent and repeatable results.
Socket Fusion

Involves heating the outside of a pipe and the inside of a fitting, then inserting the pipe into the fitting, creating a secure joint when the material cools.


  • Suitable for small-diameter pipes and fittings.
  • No need for external clamps.
  • Creates joints that are resistant to pull-out forces.

Involves connecting two ends by sliding and coupler over the ends. The coupler has coils inside that are heated up to make a leak-free pressure rate weld.


  • Provides a strong, continuous connection.
  • Suitable for creating complex shapes and custom profiles.
  • Great for tight area repairs

When to Use Saddle Fusion

Saddle fusion finds applications in various industries, including plumbing, irrigation, and industrial piping systems. It is particularly useful in scenarios where a branch connection needs to be added to an existing pipeline without disrupting the entire system.

Benefits of Saddle Fusion

Saddle fusion offers several advantages that make it a preferred choice for many applications:

  • Precision: Saddle fusion offers a precise and controlled fusion process, ensuring a reliable joint without compromising the integrity of the pipes.
  • Versatility: Compatible with various thermoplastic materials, saddle fusion proves versatile for a wide array of applications.
  • Reduced waste: The focused heating technique minimizes material waste, making it an environmentally and economically sound option.

Contact US FUSION’s Pipe Fusion Experts

Saddle fusion emerges as a valuable addition to the repertoire of pipe fusion techniques. Its unique characteristics make it well-suited for specific applications, offering a precise and efficient means of joining thermoplastic pipes.

If your project requires any type of on-site plastic fusion work, the US FUSION team is here to serve you. Our technicians are ASME Section IX certified and have nearly four decades of HDPE and welded plastic pipe fusion experience. Get in touch to learn more about how we can help, or request a free quote online here.

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