The Gas Piping System from Meter to Appliance for Non-Gas Trades
Why this matters
Gas pipe runs through the same basements, crawlspaces, attics and garages every trade works in, and it is built to stay tight for decades as long as nobody leans on it, hangs things from it, or buries the fittings that must stay reachable. When a joint starts to leak, it is usually because something stressed it, and the trade that stressed it is rarely the one that gets the call. This card is the layout and the rules of contact. It is not a gas fitting lesson.
If you smell gas or hear a hiss: act first
- Everyone leaves immediately. Do not operate any switch, light, appliance, doorbell, garage opener or phone inside. Do not start a vehicle in an attached garage.
- Leave doors open as you go if that is on your way out; do not stay to open windows.
- Call the gas utility's emergency line or 911 from outside, well away from the house, and keep people away until they arrive.
- Do not try to find the leak. That is the utility's or a licensed gas fitter's job with the right instruments.
- The meter valve is for emergencies and for people who can reach it quickly from outside. Some utilities ask the public to leave it alone and wait for them; follow your local utility's guidance. If it is closed, nobody turns it back on except the utility or a licensed fitter, because every pilot downstream has to be relit and the system checked.
The layout
OUTSIDE INSIDE
service riser main line
| |
[METER VALVE] 1/4 turn +-- branch --+
| | |
[SERVICE REGULATOR] | drop to appliance
| steps pressure down | |
[METER] ---- house piping ---->+ [SHUTOFF VALVE]
(black steel, CSST, | |
or copper in some areas) | tee ---+--> connector
| | to appliance
| SEDIMENT TRAP
| (capped stub
| below the tee)
more branches
Service line and meter. The utility's pipe arrives underground, rises to the meter, and passes through a service regulator that steps distribution pressure down to house pressure. For most natural gas homes, house pressure is a few inches of water column, on the order of a quarter of a pound per square inch. Some homes run an elevated pressure, commonly 2 psi, with a second regulator inside near the appliances. Propane homes have their own regulators at the tank and the house; see related: Propane Homes: What Every Trade Should Know.
Meter valve. A quarter-turn valve on the riser before the meter. The handle or tang lines up with the pipe when open and sits crosswise when closed.
House piping. From the meter, a main line runs to the area of the appliances and branches off to each one. Older homes are almost all black steel with threaded joints. Newer homes often use corrugated stainless steel tubing (CSST) with a yellow or black jacket, run like flexible cable and joined with fittings at manifolds and appliances. CSST has its own bonding requirement because a lightning-induced current can arc through it; see related: Yellow CSST and the Bonding Question.
Appliance shutoff valve. Every appliance has a manual shutoff in its supply. The model fuel gas codes (IFGC 409.5.1 in the 2021 edition, as adopted, and its NFPA 54 counterpart) want it in the same room as the appliance and within 6 feet of it, accessible.
Sediment trap. A short capped pipe pointing down below a tee near the appliance, so debris and moisture drop out before reaching the controls. It looks like a dead-end stub. It is not, and it must not be removed.
Appliance connector. The final link between the shutoff and the appliance, often flexible for a range or dryer. See related: Appliance Gas Connectors and Why Other Trades Should Not Move Them.
What you may operate and what you may not
You may close an appliance shutoff valve on your way out when you smell gas at that appliance and the valve is directly in reach, or when the homeowner asks you to; it stays closed until a licensed fitter or the utility has checked the appliance and relit it. Close the meter valve only in an emergency per the block above.
You may not loosen, tighten, disconnect, reconnect, cap, relocate, extend or bend any gas pipe or fitting, remove a sediment trap, or cover a valve or union where it cannot be reached. Where your state or locality licenses it, gas piping work requires a licensed plumber or gas fitter, and often a permit and pressure test.
Rules of contact
Never support anything from gas pipe. No cable straps, no hangers for ductwork, no clothes hangers in the laundry room, no shelf brackets, no sagging lumber leaning on it. Threaded joints are sealed by thread compound or tape and the tightness of the threads, and a load that flexes the pipe works those joints loose over months. A joint does not have to fail dramatically; a slow leak at a fitting in a closed ceiling is the dangerous kind. Electrical cable strapped to CSST also puts a current path right against tubing that is sensitive to arcing.
Keep valves and unions reachable. The fuel gas codes do not allow unions, certain compression fittings and similar joints in concealed locations (IFGC 404.3 in the 2021 edition, as adopted). The definition of concealed in that code treats a space behind a readily removable panel or door as not concealed, which is why an access panel is the usual answer.
Do not use it as a step or a grab. In crawlspaces and attics, gas pipe is at exactly the height a person uses to pull themselves along.
Do not heat it. No torch near it, no heat gun on the paint around it, no welding sparks landing on CSST jackets.
Do not paint over labels or the CSST bonding clamp. The clamp and its label are inspection items.
Worked example: finishing a basement ceiling
A handyman shop has a basement ceiling to frame and drywall, 24 by 30 feet. Before framing, the lead walks the gas piping and lists every gas item in or near the ceiling plane:
- A 3/4 inch black steel main running 26 feet along the ceiling, hung from the joists on pipe hangers.
- A drop to the furnace, with its shutoff valve, sediment trap and union about 4 feet above the floor beside the furnace.
- A drop to the water heater, the same arrangement beside the heater.
- A 1/2 inch branch running across six joists to the laundry, with a union in the ceiling where it was added years later, then a drop to the dryer's shutoff valve.
- A capped tee in the ceiling with a shutoff valve and a plug, left from a range that used to be in a basement kitchen.
- Three wire hangers and a closet rod hung from the dryer branch, plus two cables zip-tied to the main.
Sort them. Items 2 and 3 sit below the new ceiling and stay exposed, nothing to do but keep clear. Item 1 can be enclosed if it is running in a straight run with no fittings that the code keeps out of concealed spaces, and the lead confirms the main has only threaded couplings and tees along its length. Item 4 has a union in the ceiling: if the drywall covers it, it is a union in a concealed location. Item 5 has a valve that must stay accessible. Item 6 is loads on gas pipe.
The plan.
- Two access panels: one under the union in item 4, one under the valve and plug in item 5. Each sized so a fitter can get a wrench on the fitting, which in practice means a panel at least a hand-span wide on each side of the fitting.
- Clothes rod and hangers off the dryer branch, replaced by a rod mounted to the joists 12 inches away from any gas pipe.
- The two cables zip-tied to the main reported to the customer for the electrician, who restraps them to framing. The handyman does not cut the ties himself if doing so leaves the cables loose and hanging in the work area; he points them out and lets the electrician restrap them.
- A note to the customer that the capped range outlet in item 5 is a gas fitter's decision: whether it stays, is capped properly, or is removed back to the main.
The tally. Six items. Two need nothing. One, the main, can be enclosed as found. Two need an access panel each. One, the loads, is removed by the crew (the rod and hangers) and reported for the electrician (the cables). The ceiling plan gains two panels and loses a closet rod, and nothing gas-related was touched with a tool.
The other version. The ceiling goes up flat. The union and the valve are behind drywall, and the next fitter who needs them cuts a hole in a finished ceiling to find them. If the union starts to leak, there is no way to see or reach it, and the smell comes through the light fixtures.
What changes the answer
You find a leak while working. A faint smell near a fitting is still a leak. Follow the safety block. Do not test with a flame, ever.
The pipe is rusted, pitted or bent. Heavy surface rust on black steel in a damp crawlspace, a dent where something hit it, or a pipe with visible sag between hangers all go to the fitter as findings, with a photo.
It is an abandoned line. You cannot tell that from looking. A capped line may still be live to the cap.
How to verify you got this right
- Every shutoff valve and union in your work area is visible or behind an access panel when you leave.
- Nothing is hung from, strapped to, resting on or leaning against gas pipe.
- The sediment traps are still in place.
- Any finding is handed to the customer in the fitter's words, with location and photo. See related: Describing a Problem in Another Trade's Own Words.
References
- International Fuel Gas Code, 2021 edition, Sections 404.3 and 409.5.1, as adopted by your jurisdiction, and NFPA 54 (National Fuel Gas Code) where your jurisdiction uses it instead.
- Your gas utility's emergency guidance on gas odor and meter valves.
- See related: Yellow CSST and the Bonding Question
- See related: Propane Homes: What Every Trade Should Know