How Do I Extend the Exhaust on My Generator? + DIY Guide

Exhaust from your generator can be a concern if it is in an enclosed area.  As the generator runs, the fumes from the exhaust create carbon monoxide.  Carbon monoxide is colorless and odorless.  As with a vehicle, these fumes can be toxic, if not deadly. 

Extending the exhaust on your generator can provide the safety measure to direct dangerous fumes to a well-ventilated place.  By extending the exhaust into an open-air area, you will have peace of mind that you and your family will be protected and safe.

It is recommended that generators not be installed or run in your garage primarily due to the exhaust.  Placing the generator in an exterior shelter poses a need to extend the exhaust.  This helps keep the enclosure safe as carbon monoxide is also flammable.

There are a few options for extending the generator exhaust.  Exhaust extension kits are available to purchase, a technician can install, or you can choose a full DIY option and purchase the parts you will need. We will cover both here.

Unless you hire a technician to do the work, you’ll want to perform some preliminary steps before determining which option you feel most comfortable choosing.

How to Build a DIY Generator Exhaust Extension

Tools you may need:

• Ruler/tape measure
• Vernier caliper (recommended)
• Screwdriver, and/or
• Small socket
• Drill (possibly for exterior hole in shelter)

Measurements You’ll Need

• Measurements.  Knowing the exact dimensions of the generator exhaust is critical to either purchasing the right extension kit or getting the parts for your DIY project. 

• The generator exhaust diameter measurement must be accurate.  If your parts do not match the project will be ended before you begin.

• The length of the extension is also an important measurement.  How long does the extension need to be to route the exhaust safely from the generator to the outside?  It should extend several inches away from the shelter into open air.

• While using a ruler can give you a good measurement, using a vernier caliper provides an accurate number. 

• Be sure to give an allowance of 0.07 centimeters for the extension.  This makes sure that the extension fits securely but not too tight that you have trouble getting it on.  Don’t worry about leaks, as you will use a clamp-like device to secure it.

• Determine the right extension.  The measurement you took of the generator exhaust is what you will use to choose the extension tube or pipe.  There are two types of generator exhaust extensions.  One is a flex tube and the other is a steel non-flexible pipe.

• The flex tubecomes in varying lengths and dimensions.  The flex tube is metallic, so it will not melt with the heat of the exhaust. 

This the most common choice as it is durable for many hours of use and can be purchased at an auto parts store or online through Amazon.

Walker Exhaust 36326 Pipe-Flex Kit

• The steel pipe comes in different grades and prices.  Unless you have the tools to bend pipe, it should be installed straight from the generator exhaust to the outside of your shelter. 

Like the flex tube, steel pipe can be purchased at an auto parts store or online through Amazon.

Once you have the measurements and have determined what type of generator exhaust extension you will install – purchase a kit or DIY – you are ready for the next step.

For a DIY visual installation of your generator exhaust extension, watch this YouTube video:

How to Attach Your Flex Tube

• Cleaning the generator exhaust.  If you have previously run your generator you will need to clean the generator exhaust before installing the extension.  Carbon and oily grime need to be wiped or washed off before installing the new parts.

A clean surface helps the new parts fit securely and can avoid future loosening.

• Install the clamp.  A pipe clamp will firmly secure the extension tube to the exhaust.  There are two types of clamps on the market.  The pipe clamp and the hose clamp.  The pipe clamp is recommended for this purpose and works best with the flex tube.

Loosen the two screws on the pipe clamp with a socket or screwdriver to allow it to easily slide onto the generator exhaust.  Leave room for it to slide onto the flex tube as you place it around the generator exhaust. 

• Attach the Extension.  If you properly measured and purchased the right size tube, installation should be easy.  Slide it securely onto the generator exhaust.  Remember that the tube should be slightly larger than the exhaust by no more than 0.07 centimeters.

Slide the pipe clamp over the flex tube.  You will need a socket or screwdriver to tighten the screws on the pipe clamp.    Tighten enough that when you jiggle the extension it does not come off.  Do not overtighten as that can damage the exhaust pipe and/or extension flex tube.

• Extend through shelter wall.  Some shelters come with pre-drilled holes for the exhaust, but you may need to create that opening.  It should be level with the generator exhaust so the extension can easily pass through. 

Make sure that the material surrounding the exhaust opening is non-flammable, as the exhaust extension will become hot (between 300 and 500 degrees) when the generator is running.

Testing Things Out

The next to the last step is to run the exhaust extension to the well-ventilated distance you measured at the beginning of the project.  Remember that it minimally should extend several inches beyond the shelter.  It should be well away from windows and doors leading to avoid any draft that could carry the carbon monoxide inside.

• The final step is to test the generator exhaust extension.  This will ensure that your work has been done correctly to avoid future issues.

• Turn on the generator and allow it to run for 10 minutes.

• Check for any leaks in the flex tube at the installation site and where it extends to the outside.  Are there any exhaust odors that linger due to poor ventilation?

• Does the extension stay on securely?

Congratulations!  If all is secure, you have successfully installed your generator exhaust extension.

Additional thoughts:

Some think that installing a generator exhaust extension further reduces the sound.  It does not unless you install sound baffles or a muffler, too.  Remember that it is an extension from the exhaust, not a muffler.  If you are trying to reduce generator noise you should look into building or buying a generator quiet box. The sound from your generator will travel through the tubing or pipe.

If your generator is permanently in place (in a shelter, for example), there should be no need to disconnect the exhaust extension, unless it causes a trip hazard.  However, if the generator will be moved or stored between uses, you will want to remove the extension.   This will help the generator fit in the storage location more easily.

You will do this by untightening the pipe clamp screws and removing the flex tube extension.  Use caution when storing the flex tube to keep it from being damaged.

FAQ