UPC 1215: Sizing Fuel Gas Piping

Section 1215 is titled Required Gas Piping Size:

1215.0 Required Gas Piping Size

This falls in Chapter 12 of the UPC, which covers fuel gas piping. The section gives the method for sizing a line so it can carry the full load. It is a different job from testing the line for leaks. That test is covered in UPC 1213 on gas piping testing.

Sizing starts with demand. Each gas appliance has an input rating in BTU per hour (British thermal units). Add up the ratings of all the appliances the line will feed. That total is how much gas the pipe must deliver. The code often works in cubic feet per hour (CFH), which is just the same demand stated as a volume of gas.

Next comes length. The farther gas travels, the more pressure it loses to friction along the pipe wall. So a long run needs a wider pipe than a short run for the same load. The code sizes each section using the longest length of pipe from the gas meter or regulator to the most distant appliance.

The code lists more than one way to do this. Its subsections are headed:

1215.1 Pipe Sizing Methods 1215.2 Sizing of Gas Piping Systems 1215.3 Sizing Equations 1215.4 Sizing of Piping Sections

The most common way is to read a sizing table. You look up the pipe length and the demand in CFH, and the table gives the smallest pipe diameter that works. The tables change with the type of gas and the pipe material, so the code splits them:

1215.2.1 Natural Gas Piping Systems 1215.2.2 Propane Piping Systems

Natural gas and propane carry different amounts of energy per cubic foot, so each gets its own tables. The code also allows sizing equations for cases a standard table does not cover. The exact CFH values, pipe sizes, and pressure-drop figures live in the code tables, so they are described here, not printed.

Homes here often add gas load over time. A new pool heater, a fire pit, a gas range, or a second water heater all pull from the same system. A line that was fine for one appliance can be too small once you add another. So when you extend or tap a gas line, the plumber has to re-check the whole run against Section 1215, not just the new branch. The pipe is then installed under UPC 1210 gas piping installation.

If you are planning gas work, the pipe size is not a guess. It is math based on your appliances and your layout. This is one reason gas work needs a licensed plumber and a permit. For price, see the cost to add a gas line. For who may do the work, see the gas line permit rule in Arizona. Weighing fuel types is covered in gas versus electric water heaters. The pipe itself may be black iron or flexible CSST gas tubing, and a gas pressure regulator sets the pressure the sizing assumes.

UPC Section 1215 is part of the Uniform Plumbing Code. IAPMO publishes it and holds the copyright. The UPC viewer shows the section headings, not the full rule text, so only the headings are quoted here and the method is paraphrased. The specific sizing tables, CFH values, and pipe diameters are described, not quoted, because they are not shown on the viewer. Phoenix enforces the 2024 UPC with local amendments. Read the section on the UPC viewer at UpCodes, review the official code at IAPMO, or confirm local amendments with the City of Phoenix Planning & Development Department at phoenix.gov/pdd.