How to Install a Garage Heater with a Gas Line and Proper Venting

Last Updated on May 14, 2025 by Chad Peterson

Do you need practical information to install a garage heater with a gas line and venting? Learn all the steps and code requirements to do it right the first time.

What’s Involved in a Garage Heater Installation

Installing a garage heater isn’t just about mounting the unit on the wall and flipping a switch. You’ve got to plan for four key parts of the job:

• The heater itself
• The gas line installation
• The venting system
• The electrical power

Each part comes with its own safety rules, sizing needs, and code requirements. Some homeowners can legally do the work themselves with required permits, while others may need licensed help, especially with gas piping and venting through walls or the roof.

If done right, this install can make your garage a warm, usable space all winter long. But it’s not something to guess at. Even if you’re confident with tools, you’ll want to take it step by step, follow the rules, and double-check everything.

Can You Install a Garage Heater and Gas Line Yourself?

For many homeowners, installing a garage heater is a smart upgrade — especially in cold climates or workspaces. The big question is whether you can do the gas and venting yourself.

The short answer? In many areas, yes, a homeowner can legally run the gas line and install the heater — if you follow building codes, pull the proper permits, and pass inspection.

That said, some cities or counties require a licensed contractor for any gas work. Always check with your local building department before starting.

Planning Your Garage Heater Installation

Installing a garage heater takes more than just picking one up at the store and bolting it to the ceiling. It starts with knowing how much heat you need, where to mount it, and how your gas line and vent will route through your garage.

Proper planning saves time, avoids code violations, and helps the heater run safely and efficiently. Before you run pipe or cut vent holes, take time to sketch out your layout and double-check your measurements.

Choosing the Right Size Heater for Your Garage

• Garage size (square footage and ceiling height)
• Insulation level
• Climate zone

For a basic rule of thumb, many garages need 30 to 60 BTUs per square foot, depending on insulation and location. Under-sizing the unit means it’ll run nonstop, while oversizing could short-cycle and wear out faster.

Best Location for Mounting the Unit

Install the heater where:

• Airflow won’t be blocked
• It can reach the main area you’re trying to heat
• Gas line and venting runs are as short and direct as possible
• Clearances from combustibles meet the manufacturer’s specs
  

Corner mounting or along the front wall facing the garage door is common — but every setup is different. You may also need to factor in ceiling joist direction, lighting, or shelving.

Running the Gas Line Safely and to Code

The gas line is one of the most important parts of your garage heater installation — and it’s the one most likely to get flagged during inspection. Whether you’re using black iron pipe, CSST, or PE pipe for underground, your materials and methods must meet local code.

Sizing the pipe correctly and installing shutoffs, supports, and sediment traps is just as important as making tight connections. Gas work leaves no room for guessing.

Tools and Materials You’ll Need

Basic tools include:

• Pipe wrench or adjustable wrench
• Pipe threader (if not buying pre-threaded)
• Thread sealant or gas-rated Teflon tape
• Leak detection solution or soapy water
• Pressure test gauge (for inspection)

Materials vary depending on your setup but usually include:

• Black iron pipe and fittings (most common)
• Gas shutoff valve
• Sediment trap (“drip leg”)
• Pipe supports or clamps
• Unions for service access

Choosing Between Black Iron, CSST, or PE Pipe

• Black iron is the standard — durable, affordable, and widely accepted by inspectors.
• CSST (Corrugated Stainless Steel Tubing) is easier to route but often requires bonding and may not be allowed for outdoor or high-BTU use.
• PE pipe is used for underground runs and must be used with a tracer wire for locating later.

Sizing the Pipe for BTU Load

Proper gas pipe sizing is critical. If your pipe is too small, the heater won’t get enough fuel — leading to poor performance, frequent shutdowns, or burner problems. If it’s oversized, you’re spending more on materials and making installation harder than it needs to be.

To size the pipe correctly, you need to know:

• The BTU rating of your garage heater
• The length of the pipe run
• The number of elbows/fittings
• If any other appliances are sharing the line

Use a gas pipe sizing chart (often found in the code book or heater manual). For black iron pipe, a ¾” line can usually handle up to 150,000 BTUs over 30 feet. A typical garage heater is around 40,000 to 75,000 BTUs — but always check.

Installing the Gas Heater Vent Pipe

Venting your garage heater is just as important as running the gas line. It removes combustion gases like carbon monoxide and ensures the unit operates safely and efficiently. The type of vent you need depends on the heater model and local codes.

Some heaters use a B-vent (natural draft) system, while others are direct-vent or power-vented. Each has different clearance requirements, vent pipe types, and termination rules.

Types of Vents — B-Vent vs. Direct Vent

• B-Vent: Uses a double-wall pipe and relies on natural draft to pull exhaust up and out. Must exit through the roof and have proper vertical rise.
• Direct Vent: Sealed system that brings in outside air and vents exhaust through a wall. Great for tight or well-insulated garages.
• Power Vent: Uses a fan to push gases out horizontally. Often found in high-efficiency units.

Vent Pipe Clearance and Roof/Wall Penetrations

Keep at least 1-inch clearance from combustibles (check your local code — some require more). When going through a roof or wall:

• Use roof flashings or wall thimbles
• Seal exterior gaps with high-temp silicone or flashing tape
• Maintain proper slope and length limits

Testing for Leaks and Checking Operation

Once the gas line and vent are installed, it’s time to test everything before firing up the heater. Don’t skip this step — it’s where safety matters most.

You’ll need to do two tests:

1. A gas leak test
2. A function test after startup

Pressure Testing the Gas Line

Before connecting the line to live gas, use a manometer or pressure gauge to perform a test with air — not natural gas. Most inspections require the line to hold pressure (often around 10 psi) for a specific time with no drop.

Make sure:

• All connections are tight
• Shutoff valves are closed
• You’re using thread sealant rated for gas

Checking for Gas Leaks and Safe Operation

Once the pressure test passes and the gas is turned on, check every joint using:

• Commercial leak detection solution
• Or a spray bottle with dish soap and water

If you see bubbles, you’ve got a leak — shut off the gas and tighten the fitting.

After that:

• Light the heater according to the manual
• Confirm it cycles on/off
• Check for proper flame and blower function
• Make sure the vent is exhausting properly

Common Mistakes to Avoid

Installing a garage heater with a gas line and venting can go smoothly — if you plan ahead and follow code. But there are a few common mistakes that can cause delays, inspection failures, or worse.

Under sizing the Gas Line

Running pipe that’s too small for the heater’s BTU rating is one of the most common errors. It may technically “work,” but not safely or efficiently. Always size the pipe based on total BTUs and pipe length.

Skipping the Drip Leg or Shutoff Valve

Code usually requires a drip leg to catch debris or moisture before it enters the appliance, and a manual shutoff valve within reach of the unit. Forgetting these will likely fail inspection.

Not Bonding CSST Properly

If you’re using flexible gas tubing (CSST), it often requires a bonding clamp and wire to prevent damage from lightning or electrical surges. Missing this is not just a code issue — it’s a fire hazard.

Improper Venting or Clearance

Running vent pipe too close to combustibles, through unapproved spaces (like attics), or skipping wall/roof clearances can be dangerous. Always follow the venting instructions in the heater manual.

Not Pulling a Permit

Even if your area allows DIY work, skipping the permit is a gamble. It can void insurance claims, delay future home sales, and leave you liable if something goes wrong.

Final Thoughts — Is This a DIY Project or Better Left to a Pro?

Installing a garage heater with a gas line and venting isn’t impossible — but it’s not light weekend work either. You’ll need the right tools, solid planning, a willingness to follow code, and maybe a bit of patience when dealing with inspectors.

For skilled homeowners who are comfortable with piping, measuring, and cutting — this is doable. Just don’t cut corners. Safety is everything when working with gas and combustion.

If you’re not confident in one part of the job (like threading black iron pipe or routing a vent through the roof), there’s nothing wrong with hiring help for that step.