How to Run CSST Gas Tubing to a New Appliance

Why this matters

Corrugated stainless steel tubing (CSST) is fast to run, which is why it is everywhere and why it fails in the same few ways: a jacket stripped back too far, a fitting made on a cut that wandered off the valley, a run through framing with no striker plate where the next trade's drywall screw finds it, and tubing installed with no bonding where the maker requires it. Every one of those holds a pressure test on the day. The striker plate and the strip length are the parts of this job the inspector may never see once the wall is closed, so they are the parts the plumber owns completely.

Licensing first. This is fuel gas work. Do it only where your state or locality licenses plumbers for gas piping and your license covers it, and with a permit where one is required. The CSST maker's installation guide is part of the listing (tubing listed to ANSI LC 1/CSA 6.26), and most makers also require the installer to hold their training credential for that product line. Carry the current guide for the brand on the truck.

What this card covers and what it does not

This card runs one new branch of CSST from a spare port on an existing manifold to the shutoff valve for a new appliance. Three neighbors own the rest:

• Tube size for the run length and load comes from Gas Line Sizing for an Added Appliance. This card takes the size as given.
• Bonding of the CSST system, and what the maker and the code require of it, is CSST Bonding Verification.
• The pressure test and leak check of the finished branch is Gas Line Pressure Test + Leak Detection SOP.

Start state

Before you touch the manifold:

1. Confirm the system pressure. A low-pressure system delivers appliance pressure straight to the manifold. An elevated-pressure system (commonly 2 psi) has a regulator ahead of the manifold. Branches downstream of it are still low-pressure runs, but the added load also has to fit the regulator's capacity and the 2 psi line feeding it, and the test pressure the SOP calls for can differ. Read the regulator tag; do not assume.
2. Confirm the port is spare and capped, and trace it to the manifold that serves it. A plug that looks spare can be a port someone abandoned upstream of a leak.
3. Confirm the appliance's input rating and its connection size on the data plate or spec sheet, and the location of its shutoff. In the IFGC, as adopted, Section 409 requires the appliance shutoff to be accessible and in substance in the same room within a short distance of the appliance; check the adopted edition for the distance.
4. Have the maker's cutting tool, fittings and striker plates for that brand. Fittings and plates do not cross between CSST brands, and a fitting from another line on this tube is not a listed joint.

The run, step by step

1. Plan the route on paper before drilling. Walk it from the manifold to the appliance, measure, and add slack for bends and for the fittings at each end. Keep the route away from where it will be crushed, nailed or rubbed: not behind a dishwasher's vibration, not on the face of a stud where a cabinet screw will land, not across a sharp sheet-metal edge. Mark every place it passes through framing, because each of those gets a protection decision in step 8. Skip it and you find the conflict with a coil already cut.
2. Shut off and lock out the gas before opening the manifold port. Close the manifold's supply valve or the house valve upstream, tag it, and confirm downstream appliances have gone out. Open the port's cap slowly to bleed what is in it, with no ignition source in the room and the space ventilated. The isolation is restored in step 9 and not before.
3. Drill the framing within the structural limits. Bored holes in studs and joists have size and edge-distance limits in the adopted residential code (the IRC framing sections, as adopted); a hole oversize in a bearing stud is a structural repair. Hazard: before drilling a wall or floor you cannot see into, check for wiring, other piping and ducts on the far side, and wear eye protection against chips.
4. Pull the tubing without kinking it. Uncoil it, do not spiral it off the roll, and keep every bend at or above the maker's minimum bend radius from its guide for that size. A kink narrows the bore and can crack the stainless wall in a way the jacket hides.
5. Cut square in a valley with the maker's cutter. Use the tubing cutter the guide names, with a sharp wheel, and cut in the valley between two corrugations, light pressure, full turns. A cut on a crest or a cut that tracks crooked leaves a ragged end the fitting cannot seal against. Hazard: the cut edge of the stainless is sharp; handle it with gloves.
6. Strip only the jacket length the maker calls for. The guide gives it as a count of corrugations or a length for each size. Strip with a utility knife, cutting away from yourself, without scoring the stainless. Too little jacket off and the fitting cannot seat; too much and bare corrugation sits outside the fitting with no jacket over it, which most makers do not permit because the jacket is the corrosion and abrasion protection.
7. Make up each fitting by the maker's method. Every brand differs: some seat a split ring in the first valley, some flare the corrugation against a seat, and the guide says how far to tighten (a torque figure, a number of turns past snug, or a visual stop). Back up the fitting body with a second wrench so the torque goes into the joint, not into the manifold or the valve. Never use thread sealant on the CSST seal itself, only on pipe threads where the guide says to.
8. Protect at framing, then support. Wherever the tubing passes through or rests against framing where a fastener could reach it, fit the maker's striker plate (the maker's own hardened plates, not a generic nail plate). The fuel gas code's (IFGC or NFPA 54, as adopted) protection rule for piping near the edge of framing, in the adopted edition's Chapter 4, sets a minimum; the CSST maker's guide adds its own rules for where plates and flexible steel conduit go, and is usually stricter. Then support the run to the maker's spacing table, which increases with tube size, with the clips it calls for.
9. Test, connect, leak check, restore. Pressure test the new branch per the gas line test SOP. Then open the manifold supply, leak check every new joint with a leak-detection solution or an electronic detector, never a flame, and purge air from the branch to the outdoors or by the method in the adopted fuel gas code, with no ignition sources nearby. Relight every pilot that went out in step 2 and confirm each appliance on that manifold lights and runs. The isolation is not restored until the last one is back.

  NEW CSST BRANCH, BASEMENT MANIFOLD TO KITCHEN RANGE

  KITCHEN WALL CAVITY
                   +--[SP]--> range shutoff valve
                   |   stud face pass, tube 1 in
                   |   behind face (striker plate)
                   |
                   |  CSST up cavity, 2 ft
                   |
   ==============[SP]=====  subfloor + bottom plate
                   |          (bored 1-1/4 in, plate)
  BASEMENT         |
   joist bay, 18 ft|
   manifold -------+
   port 4 (supply valve closed and tagged)

  SP = maker's striker plate at each framing pass

Worked example: a range added on a 2 psi system

The site. A homeowner is converting an electric range to gas. The house is on an elevated-pressure system: the regulator tag beside the basement manifold reads 2 psi in, with the appliance-pressure outlet feeding the manifold. Port 4 on the manifold is capped and spare; the other three serve a furnace, a water heater and a dryer.

The size. Run through the sizing SOP for the range's rating and the run, the branch came out as 1/2 in nominal tubing. That number belongs to the sizing card; this one takes it as given.

The route. From port 4 along a joist bay for 18 ft, up through a 1-1/4 in hole bored in the center of the subfloor and bottom plate behind the range location, up the wall cavity 2 ft to the shutoff, which sits low in the wall behind the range: 18 plus 2, or 20 ft of run, plus 2 ft of slack for the bends and the fittings, so 22 ft cut from the coil.

Shutoff. Manifold supply valve closed and tagged. The water heater and furnace pilots and burners went out within a minute, confirmed by looking. The dryer was idle. Port 4 opened with no ignition source in the basement.

Fittings. Manifold end: cut in a valley, jacket stripped to the count in the guide, fitting made up with a backup wrench, tightened to the guide's stop. Valve end: the first strip ran two corrugations long, leaving bare stainless outside the fitting nut when the fitting was assembled loosely to check. Stop. Cut back one valley beyond the over-strip, stripped again to the guide's count, made up. The fitting nut now covers the stripped section with jacket running into it.

Protection. Two framing passes: the bored subfloor and bottom plate, and the top of the 2 ft rise, where the tube turns toward the valve against a stud face. A striker plate went at each. The wall pass was the one that mattered; the tube sat about an inch behind the face of the stud where the cabinet installer's screws would land.

Test and restore. The branch was tested by the gas test SOP and held. Supply valve opened. Both new fittings and the port connection were leak checked with solution: no bubbles. The branch was purged at the range connection to the outdoors through a hose, away from any ignition source, until gas reached the end. The furnace and water heater were relit and seen burning; the dryer was run for a cycle. The range was connected by the appliance installer with a listed connector and lit on all burners.

What would change it. The branch itself sizes the same on a low-pressure system with no regulator, because a manifold downstream of a regulator sees appliance pressure either way. What differs is upstream: with no regulator, the added load rides the low-pressure line all the way from the meter, which the sizing card checks from the meter; on this 2 psi system, it confirms instead that the regulator covers the range on top of the other three appliances. If the range went on an island, the route crosses an open floor with no wall cavity, and the protection decision moves to where the tube is exposed under the cabinet base.

How to verify you got this right

• No bare corrugation shows outside any fitting, and every fitting was made with the brand's own parts.
• A striker plate sits at every framing pass where a fastener could reach the tube, and the run is supported to the maker's table.
• The test held, every joint passed the leak check with solution or a detector, and every appliance on the manifold was relit and seen running.
• The bonding question is closed on the ticket by CSST Bonding Verification, not assumed.

References

• IFGC 2021 or NFPA 54, as adopted by your jurisdiction: Chapter 4 protection of piping and Section 409 appliance shutoff valves.
• IRC 2021 framing sections, as adopted: limits on bored holes in studs and joists.
• The CSST maker's installation guide and training requirements for that product line (ANSI LC 1/CSA 6.26 listed tubing).
• See related: Gas Line Sizing for an Added Appliance; CSST Bonding Verification; Gas Line Pressure Test + Leak Detection SOP.