Gas piping for a commercial kitchen has to be sized for every appliance on the line running at once, and it has to be permitted, pressure tested and inspected before the gas goes on. Most kitchen gas problems we see start with a line that was right for the original equipment, then had appliances added until the burners at the end of the line starved.
How a kitchen gas system is laid out
Gas comes from the utility's main, through the utility's service line and meter, and into the building's own piping. In the St. Louis area that utility is usually Spire. Everything past the meter belongs to the building owner. Spire's Missouri tariff says so directly: pipe and equipment beyond the company's meter is installed by and belongs to the customer or owner, and has to be kept in safe operating condition at the owner's expense (Spire Missouri rules and regulations, Rule 11).
Inside the building, a typical kitchen system has:
- The main run from the meter to the kitchen, often with branches to boilers, water heaters or rooftop units on the way.
- A manifold or header along the cooking line, with a drop to each appliance.
- A shutoff valve at each appliance, so one piece of equipment can be serviced without shutting down the line.
- Connectors from the valve to the appliance. Equipment on casters uses flexible connectors made for appliances that get moved for cleaning.
- Regulators where the building gets gas at a higher pressure than the appliances use.
Sizing for the total load
Every gas appliance has a nameplate input rating in BTUs per hour. Pipe sizing starts by adding up the ratings of everything the pipe serves. Then the pipe size is picked for that total load, the length of the run and the pressure available, so the last appliance on the line still gets the pressure its burners need when everything is lit.
The rules for doing this are in the fuel gas code. Nationally, that's NFPA 54, the National Fuel Gas Code, and many local governments adopt a fuel gas code of their own. The code the building department adopted is the one your job is inspected to.
A kitchen is a hard case because it really does run everything at once. During a lunch rush, the fryers, range, griddle, ovens and steam equipment can all be firing together.
Here's a hypothetical example. Say a school kitchen's line was piped years ago for two ovens, a range and a kettle. The district now wants to add a tilting skillet and swap the range for a larger one. The new nameplate total is well above what the original pipe was sized for. It may run fine on a slow day, then on a full-production day the flames go yellow and the ovens recover slowly, and the staff blames the appliance. The real fix is a bigger branch, a new run, or higher-pressure gas with a regulator at the kitchen.
Adding or replacing equipment
Before you buy a new appliance, get its gas input rating and connection size from the spec sheet and have it checked against the existing piping. A one-for-one swap of the same size usually just needs a new connector and a test. A bigger appliance, or an added one, may need:
- A larger drop or a larger section of the header
- A new branch from the main
- A check of the meter and service capacity with the utility
- A different connector or a relocated valve so the appliance fits under the hood
If the kitchen has a hood with a fire-suppression system, ask how the new appliance ties into it. Cooking equipment has to sit where the hood and its suppression nozzles cover it, and the gas to the line is often run through a shutoff connected to that system. The hood installer, the fire protection contractor and the pipefitter need to talk before the appliance shows up.
Working with the utility
The meter and service line belong to the utility, and they were sized for the building's load when they were installed. If you add a lot of gas equipment, the meter or service may need to be upgraded too. Spire's tariff asks customers to notify the company promptly in writing of any material change in their installation or load (Rule 4). On a renovation, bring the utility in early, because a meter or service upgrade runs on the utility's schedule, not yours.
The utility can also shut off service without notice if it finds a dangerous condition in the customer's piping or equipment, and service stays off until the condition is fixed (Rules 14 and 16). Only the utility turns the gas back on at the meter once it has been shut off, according to Spire's natural gas safety handbook.
Permits and inspections
Under Spire's tariff, piping and equipment the customer installs past the point of delivery has to meet the laws and rules of the local authorities, and the customer is responsible for getting the permits (Rule 19). Who issues the permit depends on where the building is. St. Louis County and many of its municipalities run their own permit offices.
In the City of St. Louis, mechanical permits are issued only to licensed mechanical contractors certified by the City, and the City lists boilers, furnaces, exhaust fans and hoods among the work that needs one. Mechanical work there is governed by the 2018 International Mechanical Code as adopted by the City (City of St. Louis mechanical permits). Your contractor should know which office has jurisdiction and what it wants to see.
On a typical job, new piping is pressure tested before it's covered up or connected, the inspector checks the work, and then the system is purged and the appliances are lit and checked. Build the inspection into the schedule so gas work isn't finished the night before a reopening.
Safety basics for kitchen staff
- Know the smell. Natural gas has no odor on its own. Spire adds mercaptan to give it a rotten-egg smell (Spire).
- If you smell gas, leave first. Get everyone out, don't flip switches or use anything that could spark, and call Spire's emergency line at 800-887-4173 or 911 from a safe place.
- Watch the flames. Spire lists a burner flame that is yellow, wavy or higher than normal as a reason to call (gas appliance safety). In a kitchen, it can also mean the appliance isn't getting enough gas.
- Know where the shutoffs are. Every cook should know where the appliance valves are and where the kitchen's main shutoff is.
- Call 811 before digging near buried gas lines outside, such as for a new patio or a grease interceptor.
Questions to ask before a kitchen project
- What is the total BTU load of the equipment, existing and new?
- Is the existing pipe sized for it, and is the meter?
- Does the utility need to be notified or upgrade the service?
- Who pulls the permit, and when is the inspection?
- How does each appliance connect to the hood's fire-suppression system?
Kitchen gas usually isn't the only gas in the building. If you're also replacing a boiler or rooftop units, it's worth asking whether the building's heating has to burn gas at all. A geothermal system heats without it, and for a business that takes a seasonal gas bill off the table.
Next step
Planning a new kitchen, an equipment upgrade or a renovation? We pipe gas for commercial kitchen equipment, boilers and gas heaters across the St. Louis area. Request a free estimate or call 636-327-4238.