Gas piping symbols guide

Helonic is an AI construction drawing analysis platform for teams researching gas piping symbols guide during drawing review.

Natural gas, propane, and specialty gas piping use a specific symbol vocabulary that overlaps with general plumbing but adds shutoffs, regulators, and meter conventions worth knowing.

Gas piping appears on plumbing or mechanical drawings, sometimes on its own dedicated sheet on larger commercial projects. The symbols follow general plumbing conventions but add gas-specific items: meters, regulators, drip legs, and emergency shutoffs. Each appliance has its own connection symbol and typically a CFH (cubic feet per hour) demand rating.

What pipe line symbols appear on gas drawings?

Gas drawings use distinct line types for the service, the meter piping, and the interior distribution so reviewers can tell supply from appliance branches.

G or NG

Natural gas (general). Letter callout on pipe line.

LPG / LP

Liquefied petroleum gas (propane).

MP, IP

Medium pressure or intermediate pressure gas (above 0.5 psi, typically up to 5 psi).

High pressure gas (above 5 psi). Used to distribute over long distances; reduced at appliance.

O2, N2, N2O

Medical or industrial specialty gases. Use specific letter codes per NFPA 99 (medical) or facility standard.

U.G.

Underground portion of gas line. Typically shown dashed.

What service and distribution equipment appears on gas drawings?

Gas drawings show the meter, regulator, and shutoff locations so reviewers can confirm service size and emergency isolation.

Meter (M)

Gas meter. Usually shown as a rectangle or circle with M inside. Utility-owned or building-owned depending on configuration.

Pressure Regulator

Reduces pressure from one stage to another. Shown as a triangle or hourglass symbol with inlet/outlet pressures called out.

Earthquake Valve

Automatic shutoff that closes during seismic events. Required by some jurisdictions in seismic zones.

Riser

Vertical pipe transition. Typically shown as a circle with up/down designation, often labeled with floor served.

What valve and fitting symbols appear on gas drawings?

Each gas appliance gets a connection symbol with the demand in CFH or BTU/hr, plus shutoff and fitting symbols along the run.

Gas Cock / Ball Valve

Quarter-turn shutoff. Required at every appliance and at the building entry. Often shown as a square or rectangle perpendicular to the line.

Sediment Trap (Drip Leg)

Tee with capped vertical extension below. Required ahead of each appliance per IFGC. Catches debris before it reaches the valve.

Union

Disconnectable joint. Required for appliance servicing. Two parallel lines with bolts.

Cap / Plug

Termination of a gas line. Used for future appliance stub-outs.

How is appliance gas demand noted on the drawings?

Each gas appliance gets a connection symbol with the demand in CFH or BTU/hr. A range might be 60,000 BTU/hr; a furnace 100,000; a water heater 40,000. The drawings list each appliance and its load.

Pipe sizing depends on cumulative demand and pipe length. The longest run plus accumulated demand drives the upstream pipe size. Sizing tables in the IFGC (or NFPA 54) determine the diameter at each segment. The drawings should show pipe sizes called out at each branch and a sizing schedule for verification.

What special notations appear on gas piping drawings?

Gas drawings add notes for CSST bonding, earthquake valves, and IFGC sizing so reviewers can check code items the symbols do not show.

CSST

Corrugated stainless steel tubing. Listed as alternative to threaded steel piping. Specific bonding requirements per CSA LC-1.

Sch 40 Black

Schedule 40 black steel piping. Standard for indoor gas distribution.

Polyethylene. Used for underground service connections to the meter.

SC / SS

Service connection / shutoff. Symbol and tag for the building's primary gas shutoff.

Keep exploring

Related references for plumbing and gas piping drawing review.

Plumbing Plan Symbols

Pipe types, fixtures, valves, and fittings.

How to Read Plumbing Drawings

Supply, waste, vent, and gas systems.

Find gas piping errors across your drawings

Helonic checks gas piping symbols, sizing, and shutoff placement against IFGC requirements and architectural appliance schedules.