CSST Installation and Bonding Requirements

What Is CSST?

Corrugated stainless steel tubing (CSST) is a flexible, yellow-jacketed gas piping product used to distribute natural gas and propane inside buildings. Its corrugated stainless steel core makes it bendable, which reduces the number of fittings needed and speeds installation. CSST is listed to ANSI LC 1 / CSA 6.26, the standard governing flexible gas piping. Every manufacturer publishes an installation guide that is part of the code compliance package; you must follow that guide exactly, because the International Fuel Gas Code (IFGC) adopts manufacturer instructions by reference.

Safety First

Before you touch any gas piping material, review these non-negotiable rules:

• Safety glasses are required whenever you are cutting, threading, or assembling piping.
• CSST shears produce sharp metal slivers — keep fingers clear of the blade path and dispose of cut ends in a puncture-resistant container.
• Work in the de-energized, depressurized state. The system must be shut off and the line verified free of pressure before you modify any piping. Lock out and tag out the gas supply valve following your employer's lockout/tagout (LOTO) procedure.
• Never use an open flame to test for leaks during or after assembly. Use an approved leak-detection solution or listed electronic detector.
• The yellow jacket is not the bonding conductor — the jacket is a dielectric coating. Do not rely on it for electrical continuity.

Measuring and Cutting CSST

Accurate measurement prevents waste and avoids joints in concealed spaces. Measure from the end of the fitting body on one end to the end of the fitting body on the other end, then add the manufacturer's specified insertion depth for each fitting (check your installation guide — this value varies by brand and tubing size). Mark the tubing with a felt-tip pen.

Cut with CSST shears only — never a hacksaw, pipe cutter, or angle grinder. A hacksaw leaves metal fragments inside the corrugations that contaminate the system and can damage regulators or appliance valves. CSST shears make a clean, square cut through the corrugations. After cutting, inspect the end: the cut must be square, not angled, and free of jagged peaks. A jagged edge prevents the fitting from seating correctly and can cause a leak.

Fitting Assembly

CSst end fittings use a mechanical connection that compresses a sleeve around the tubing end. The exact design varies by manufacturer, so follow the installation guide step by step:

1. Slide the nut and any required components (sleeve, O-ring, etc.) onto the tubing in the correct order and orientation before inserting the tubing end.

2. Push the tubing end fully onto the fitting body until it bottoms out. An under-inserted tube is the most common installation error and will fail a pressure test.

3. Hand-tighten the nut, then apply the manufacturer's specified wrench torque or wrench-turn count. Over-tightening can crack the fitting body; under-tightening leaks.

4. Do not use pipe dope or thread tape on CSST fittings — only on the male NPT thread at the transition to rigid pipe.

Routing, Bending, and Strike Protection

CSst can be bent by hand to change direction. Observe the manufacturer's minimum bend radius (shown in the installation guide for each tubing size) — overbending kinks the corrugations and restricts flow.

When CSST passes through or alongside a framing member where a nail or screw could penetrate it, strike protection is required. The IFGC and every major manufacturer require a listed steel striker plate (also called a nail plate) over any framing member within the protection zone specified in the guide. The plate must be of sufficient gauge and must cover the full width of the member. Failure to install strike protection is a leading cause of CSST puncture fires.

Additional routing rules:

• CSST must not be in contact with masonry, concrete, or soil without protection.
• Secure the tubing with listed hangers at the manufacturer's maximum spacing.
• Keep CSST away from heat sources and sharp edges.

Bonding and Grounding Requirements

This is the most critical code topic for CSST. All CSST systems must be bonded. The requirement exists because lightning or electrical fault current that enters the gas system can arc through the thin corrugated wall, causing a pinhole leak and fire.

The IFGC and CSST manufacturer installation guides require that a bonding conductor connect the CSST system to the building's grounding electrode system (GES) or to the electrical service grounding means. Key points:

• Where to connect: Attach a listed bonding clamp directly to the CSST jacket or to an accessible metallic fitting on the CSST system. The clamp must be listed for use with CSST — do not use generic pipe clamps.
• Wire size: The minimum conductor size is specified in the manufacturer's guide and references the IFGC. A common minimum is No. 6 AWG copper, but always verify with the specific manufacturer's guide for the brand you are installing, because some brands specify larger conductors for longer runs.
• Path to ground: Run the bonding conductor to a grounding electrode, the electrical panel ground bus, or another approved point in the GES using the shortest practical path.
• One connection per system: A single bonding connection to an accessible metallic component bonds the entire continuous CSST system, because the corrugated metal core is electrically continuous.
• Jacket conductivity: The yellow polyethylene jacket is non-conductive. The bonding clamp must make contact with the metal of the tubing or fitting, not just the jacket.

After installation, document the bonding location on the as-built sketch you provide to the customer or general contractor.

Pressure Testing

After assembly and before concealment, pressure-test the system per the IFGC and local AHJ requirements. Apply leak-detection solution to every fitting and inspect visually. No bubbles equals a passing test at that joint. Record test pressure and duration per your jurisdiction's requirements.