How To Work With Gas Pipes

Gas pipes are a hidden essential for many homes, working behind the scenes to provide fuel for heating, cooking, and other appliances. However, not many homeowners know how their gas pipes work. In the video above, plumbing and heating expert Richard Trethewey shows the fundamentals of gas piping, from routing the pipes in your home to checking for leaks. Read on to learn more about gas pipes and why it’s important to hire a licensed professional for any gas piping projects.

Is Working With Gas Pipes a DIY Project?

Working with gas pipes is not something you should do yourself. As Richard Trethewey says in the video above, only licensed professionals should work with gas pipes. However, you should still know how gas piping works so that you can be aware of the infrastructure in your home and prepare for accidents like gas leaks.

The dangers of gas systems are not just theoretical. Richard Trethewey recounts the catastrophic event in Lawrence, Massachusetts, where 80 houses caught fire within a two-hour period due to a utility-wide gas pressure failure. While he notes that gas distribution is “a generally incredibly safe system,” he emphasizes that “we should be thinking about gas safety because even isolated events can be dangerous.”

Gas Pipe Sizing and Layout

The size of your gas pipes depends on a few factors, including the number of appliances you have in your home and what type of appliances they are.

Initial Sizing Considerations

Gas pipe sizing begins at the meter, where the main supply enters the home. Typically, residential houses start with 1-inch gas pipes. From there, the pipes branch out to smaller diameters using T-fittings as they reach their appliance destinations. 

The initial pipe size is determined by:

• The total gas load of all appliances
• The distance from the meter to the furthest appliance
• The allowable pressure drop in the system

Branching and Reducing Pipe Sizes

As the gas system extends throughout the home, you should reduce pipe sizes to accommodate the decreasing gas flow requirements. You can do this with T-fittings and reducers. The layout forms a tree-like structure, with larger pipes near the source and smaller pipes near the appliances. Remember:

• Larger appliances like furnaces need bigger pipes than smaller ones like stoves.
• You need to calculate pipe sizing ahead of time to get adequate gas flow to all appliances.
• Improper sizing can lead to incomplete combustion and poor appliance performance.

Pro Tip: Richard Trethewey, TOH plumbing and heating expert, explains the starting point for sizing: “Gas comes in from the street… at a particular amount of pressure. Now, by gas code, you have to figure out what size pipe… So typically in a residential application, you might have inch and a quarter or one inch pipe coming in. And now you look at the building and say, all right, what’s the size of the furnace and the water heater and the dryer? And now you have to have enough pipe size to support” all of those loads.

Types of Gas Pipes and Fittings

Gas piping systems use various materials to route and connect to the appliances in your home.

Steel Pipes

Steel pipes are the traditional choice for gas piping and are still popular today. They offer durability and strength, making them suitable for both indoor and outdoor applications.

Flexible Gas Lines

Flexible gas lines are usually composed of corrugated stainless steel tubing (CSST) and are easy to bend and route through walls, making them perfect for homes with a lot of obstacles.

Copper Pipes

Copper pipes are most prevalent in propane systems. Any time you use copper pipes, mark them to indicate the type of gas they carry.

Fittings and Connectors

Experts use a variety of fittings and connectors to join gas pipes to appliances. Common gas pipe fittings include:

• T-fittings for creating branches
• Elbows for changing direction
• Couplings for joining pipe sections
• Reducers for transitioning between different pipe sizes
• Shutoff valves for controlling gas flow to individual appliances

Measuring and Cutting Gas Pipes

Licensed professionals use various pre-cut lengths and small pipes called nipples to create the exact dimensions needed for each section of the system. When installing a piping system, they use the following steps:

1. Measure the distance between fittings, accounting for the thread engagement.
2. Select the appropriate pre-cut pipe length or nipple.
3. If necessary, use couplings to join shorter sections to achieve the desired length.
4. For custom lengths, use a pipe-threading tool to create precise threads.

Pre-cut pipes typically range from 6-foot lengths down to about 18 inches. Below 12 inches, shorter pieces known as nipples are available, ranging from 1.5 inches up to 6 inches, and from 6 inches up to 12 inches. When a standard size doesn’t match — for example, if the measurement between fittings calls for 21 inches — a coupling is used to join a standard 18-inch pipe with a shorter nipple to bridge the gap.

Joining Gas Pipes and Fittings

A tight piping connection is important to prevent gas leaks and to make sure the gas is flowing steadily. Professionals use the following steps when connecting gas pipes:

1. Apply pipe dope or thread sealant to all threaded connections.
2. Use two wrenches to tighten fittings—one to hold the pipe steady and another to turn the fitting.
3. Start connecting at the source (meter) and work outward toward appliances due to the nature of threaded connections.
4. Ensure all connections are tight but not over-tightened, which can damage the threads.

Testing for Gas Leaks

According to the United States Energy Information Administration, natural gas leaks can cause explosions, so it’s important to test for leaks during installation. Professionals use both pressure testing and soap testing methods to confirm that the new system is leak-free.

Here are some steps to perform pressure and soap tests for leaks:

1. Close the main shutoff valve.
2. Use a manometer to pressurize the pipes and wait overnight to see if the pressure drops.
3. Apply a soap solution to joints and observe for bubbles as an indication of leaks.
4. Address any detected leaks immediately through re-tightening or replacing faulty fittings.

Emergency Procedures When Working With Gas Pipes

In the event of a gas leak, it’s important to know how to respond. Homeowners should be familiar with emergency procedures to minimize risks and protect their safety.

Steps in case of a gas leak:

1. Immediately evacuate the home and move to a safe distance.
2. Avoid using any electrical devices, open flames, or creating sparks.
3. Call the gas company or emergency services to report the leak.
4. Do not re-enter the home until it has been deemed safe by professionals.

Pro Tip: Nathan, a TOH plumbing expert, keeps the advice simple and direct: “The first rule with gas is, if you smell it in the house, it’s time to get out. Get outside. Call the people you need to call. It might be the gas company, the fire department.”