How to Safely Cut CSST: Essential Step-by-Step Guide (2024)

Cutting CSST, or Corrugated Stainless Steel Tubing, requires a specific methodology and the right tools to ensure a clean, safe, and code-compliant connection. While it might seem daunting due to the unique properties of the alloy, the process is straightforward when you understand the necessary steps. This guide walks you through the precise techniques for cutting CSST, emphasizing safety and accuracy to prevent damage to the pipe wall.

Understanding CSST and Its Properties

Before making the first cut, it is essential to understand what CSST is and how it behaves. This tubing is made from a thin-walled, stainless steel alloy coated with a yellow polyethylene sheath for protection against corrosion. Because of its construction, it cannot be cut with standard steel pipe cutters or abrasive blades, as these can damage the outer sheath or introduce micro-fractures into the metal. The goal is to sever the inner metal tube while leaving the outer sheath intact and ready for a secure connection using specialized connectors.

Gathering the Right Tools

Using the correct tools is non-negotiable when working with CSST. The wrong tool will crush the pipe or leave a jagged edge that compromises the system. You will need a tool specifically designed for cutting stainless steel, which ensures a smooth cut without deforming the tube. Additionally, you will require a CSST-specific deburring tool to remove the sharp inner burr, and a specialized connector kit to complete the installation properly.

Essential Tool List

• CSST-specific cutting tool (or a 3/8-inch abrasive cut-off wheel with safety guard)
• CSST deburring/internal chamfering tool
• Measuring tape or calipers
• Marking pen or scribe
• Adjustable wrench or CSST-specific wrench

The Measurement and Marking Process

Accuracy is critical in any gas line installation to ensure proper flow and prevent strain on the connectors. Before cutting, measure the required length meticulously, accounting for the fittings that will be attached. Use a fine-tipped marker to score the circumference of the pipe. It is vital to mark the pipe clearly without scratching deep grooves into the metal, as these can become stress points. For the cleanest results, utilize a tool that scores a distinct line as a guide for the cutting wheel.

Cutting the CSST Safely and Effectively

With the pipe marked, secure it firmly in place to prevent rolling during the cut. If using a dedicated CSST cutter, align the mark with the wheel of the tool and tighten the knob until the pipe is snug. Slowly rotate the pipe one full revolution to create a uniform score. Do not force the tool; let the mechanism do the work. If using an abrasive wheel, set the tool in a vise with a guard to catch debris, and use a light touch to cut through the metal in a single, controlled pass.

Deburring and Final Preparation

Once the metal is severed, the inner edge will be sharp and jagged. This burr must be removed before connecting the fitting, as it can tear the CSST sheath or cause a dangerous leak. Insert the deburring tool into the cut end and rotate it several times to smooth the interior edge. Next, inspect the outer sheath and remove the yellow polyethylene layer approximately 1.5 inches from the end using a utility knife. The exposed metal is now ready for the installation of the connector, ensuring a gas-tight seal that meets safety standards.