Can my restaurant's gas line handle a new fryer or range?

You check the total load against the code's sizing tables. Section 402.2 of the 2024 International Fuel Gas Code, which Phoenix enforces, sets the flow as "the sum of the maximum input of the appliances served," assuming "all appliances could be operating at full capacity simultaneously." Section 402.1 then requires the piping to deliver gas "to each appliance inlet at not less than the minimum supply pressure required by the appliance."

Here's the process a plumber or designer follows:

1. 1List every appliance and its input. The rating plate on each range, fryer, oven, broiler and water heater gives Btu per hour. Include everything on the same piping, not just the cooking line, and anything you plan to add, like patio heaters or a standby generator.
2. 2Convert Btu to cubic feet per hour. Sizing tables are in cubic feet. Natural gas is roughly 1,000 Btu per cubic foot for sizing, so 100,000 Btu is about 100 cubic feet per hour. Southwest Gas's Arizona tariff says its gas averages "not less than 900 Btus per cubic foot," so use the utility's figure when the margin is tight.
3. 3Measure the longest run. The tables use the length from the meter to the most remote appliance.
4. 4Look up each pipe section. Compare the load each section carries against the table value for its size and length.

### What does that look like with real numbers?

Take a kitchen piped in 1-1/4 inch steel, with the farthest appliance 100 feet from the meter at standard pressure. Table 402.4(1), the common low-pressure table, rates that pipe at 304 cubic feet per hour. Now say the existing lineup totals about 250 cubic feet per hour.

The same table rates 1-1/2 inch pipe at 455 cubic feet per hour over 100 feet, which covers the fryer with room left. Length matters just as much as size. That same 1-1/4 inch pipe carries 442 cubic feet per hour over 50 feet but only 209 over 200 feet. A kitchen at the back of a long building can run out of capacity sooner than the same kitchen near the meter.

These numbers are an illustration. A real check follows the actual pipe sizes section by section, and the designer picks the table that matches the building's supply pressure and allowed pressure drop.

The meter has a capacity too, and it can fill up before the pipe does. Southwest Gas owns the meter, so a bigger one is the utility's job and its call. Its Arizona tariff says "It is the customer's responsibility to notify the Utility of changes in their load requirements," and that changes like "larger meter capacity" are made at the utility's option, with the customer possibly required to reimburse it. Phoenix's plan review checklist asks every gas drawing to mark the meter "as either EXISTING or NEW, documenting capacity." Our guide to getting a bigger Southwest Gas meter covers the request.

Check the last few feet too. Section 411.1.3.2 says connectors "shall have the capacity for the total demand of the connected appliance," and 411.1.3.4 says the shutoff valve ahead of it must be at least the connector's nominal size.

Hose capacity drops with length and with a quick-disconnect. Dormont's published table for its commercial connectors shows a 1/2 inch hose at 6 feet rated for 86,600 Btu straight, but only 55,000 Btu with a quick-disconnect. A 3/4 inch hose with a quick-disconnect at 6 feet is rated for 139,000 Btu. A big fryer on an undersized hose acts like an undersized pipe. Our page on gas hoses for equipment on casters goes deeper.

Symptoms show up when everything runs at once:

• Burner flames that shrink or go lazy when the fryers and ovens fire.
• Fryers or ovens that recover temperature slowly during a rush.
• Pilots or burners that drop out, or appliances that lock out on a low gas pressure switch.

A.O. Smith's commercial water heater handbook gives a useful test that applies to any appliance: measure supply pressure with everything off, then with every appliance on the line "firing at full capacity." If pressure drops more than 1.5 inches of water column as gas begins to flow, "the supply gas system including the gas line and/or the gas regulator may be restricted or undersized." The same handbook says drops beyond that "may cause rough starting, noisy combustion or nuisance outages."

A licensed plumber can run that test with a manometer on your actual line, which beats guessing.

Often, yes. The City of Phoenix gas clearance table, published with Southwest Gas and the Arizona Corporation Commission, lists "Appliance upgrade with an increase in BTU consumption requiring piping capacity calculations" as needing a permit, a city inspection and a city clearance. So does any new gas piping. A straight swap of one appliance for a similar one on its existing connector, with no piping change, does not.

The testing is lighter than for a new building. Section 406.1.3 says that when new branches go in for new appliances, "only the newly installed branches shall be required to be pressure tested," with the tie-in to the old pipe checked with leak-detecting fluid. Other Valley cities run their own permit offices and fuel gas code editions, so check the city that covers your address.

The fire side can change too. Phoenix's fire code, Section 904.14.5.1, says that when cooking equipment is added, moved or replaced under a hood, the suppression system has to meet current rules for the new lineup. That's work for your fire suppression contractor, so call them before the fryer arrives. Our page on whether a restaurant needs a gas leak inspection covers how the fire code treats a rearranged cooking line.

HQ Plumbing & Air runs load calculations, pressure checks and commercial gas line upgrades for restaurants across the Phoenix area. We'll tell you whether your line can take the new equipment before you buy it, with a free estimate and the price up front.

Add it up before the fryer shows up. That's the play.