How Many Appliances Can a ¾” Gas Line Supply?

Understanding Gas Line Sizing Basics

Gas line sizing hinges on delivering the appropriate volume of gas to each appliance while maintaining sufficient pressure.

Gas flow is measured in British Thermal Units (BTUs) per hour. Most appliances have their BTU rating listed on their data plates, which helps determine the demand.

A 3/4-inch gas line can supply between 70,000 to 200,000 BTUs per hour, depending on the pipe's length and the pressure of your gas system.

Shorter runs and higher pressure systems allow for greater capacity, while longer distances reduce flow.

Factors That Affect Gas Line Capacity

To determine how many appliances your 3/4-inch gas line can serve, you need to consider several key variables:

Gas Type

Natural gas and propane have different delivery characteristics. Natural gas operates at lower pressure and requires larger pipe sizes to deliver the same BTUs as propane.

Line Length

Longer gas lines result in more pressure loss, reducing the total flow available at the appliance. For example, a 50-foot 3/4-inch natural gas line delivers less capacity than a 10-foot line of the same diameter.

Appliance Gas Supply Requirements

Each appliance has specific BTU needs:

• A standard gas stove can use up to 65,000 BTUs per hour.
• A gas water heater has a BTU rating of between 30,000 and 40,000 BTUs per hour.
• A gas dryer typically requires 22,000 BTUs per hour.
• A gas furnace often consumes 100,000 BTUs per hour or more.

Knowing these ratings is critical when planning your gas system.

Gas System Pressure

The capacity of a gas line increases with higher pressure systems. Most residential natural gas systems operate at low pressure (around 0.5 psi), but some high-pressure systems allow smaller pipes to carry more gas.

Determining Your Appliance Capacity

Here’s a practical example of how to calculate appliance capacity:

Pipe Diameter: 3/4-inch
Line Length: 20 feet
Gas Type: Natural Gas
System Pressure: Low pressure
Using standard gas pipe sizing charts, a 3/4-inch pipe with a 20-foot run can deliver approximately 138,000 BTUs per hour. With this capacity:

A 65,000 BTU gas stove can be safely supplied.
A 40,000 BTU gas water heater could also be included.
This leaves a buffer of about 33,000 BTUs, which might power a small appliance like a gas dryer.
However, if the line length increases to 50 feet, the capacity drops to approximately 75,000 BTUs per hour, meaning it could only support the stove or the water heater, not both.

Avoid Overloading Your Gas Line

Overloading a gas line can result in underperforming appliances, inefficient combustion, and potentially dangerous conditions. To avoid these issues:

• Consult a Licensed Professional: Gas line installations must meet local building codes, which may dictate pipe sizing requirements.
• Perform Accurate Calculations: Use pipe sizing charts specific to your gas type and pressure to ensure safe and sufficient flow.
• Plan for Future Expansions: If you anticipate adding more appliances, consider upsizing the gas line now to avoid costly changes later.

When to Upgrade to a Larger Gas Line

If your calculations show that a 3/4-inch gas line can't meet your needs, upgrading to a larger diameter line is often the best solution.

For example, a 1-inch gas line can supply nearly double the capacity of a 3/4-inch line for the same length and pressure.

While this involves additional upfront costs, it ensures reliable performance and minimizes the risk of pressure drops or gas starvation.

Always consult a licensed plumber or technician for professional guidance and adhere to local building codes when installing or modifying gas lines.

Making informed decisions about gas line sizing today can save you from costly repairs and unsafe conditions tomorrow.

Frequently Asked Questions

How many BTUs is a gas dryer?

Standard gas dryers are typically rated at 22,000 BTUs per hour. The exact BTU output varies based on brand and model. Look at the rating plate on the dryer or refer to dryer specifications to find the BTUs of a specific dryer.

How many BTUs is a 4 burner gas stove?

A 4 burner gas stove with an oven can use up to 65,000 BTUs per hour when all 4 surface burners (10,000 BTUs per hour) and the oven (25,000 BTUs per hour) are in use. The exact ratings of the burners are listed in the specifications for the stove and you’ll also find the BTUs per hour output on the rating plate of the stove. When BTU/hour ratings are provided for individual burners on the stove, you’ll need to add the outputs to calculate the total BTU/hour capacity of the stove.

What size gas line for gas dryer?

A 1/2" NPT pipe is recommended for most gas dryers. 3/8" approved tubing is acceptable for lengths under 20 ft. if local codes and the gas supplier permits its use. See the installation guide for your gas dryer to find the exact gas line requirements for your brand and model.

What happens if a gas line is too small?

A gas line that is too small will limit the fuel supply to appliances, limiting their performance and/or causing them to stop working. Limited gas flow from a small gas line will weaken burner flames and lead to poor heating performance. Flames can go out and cause dangerous conditions in your home that can result in fires or explosions. Too small of a gas line can also reduce the expected life of an appliance.