How to Make an Exhaust Extension for Your Portable Generator (For Under $20)

Last Updated on July 25, 2022 by Manager Access

portable generator exhaust extension
In many situations, you will want to vent your portable generator’s exhaust away from your work area to a better-vented area.

This is vital in enclosed shops, when bringing your generator in the garage during a storm, or even for using it in your RV.

A generator exhaust extension bolts to your generator’s exhaust and allows your exhaust fumes to be routed outside of your working area.

These can be bought online in a kit for your RV, but for portable generators, you will have to get a little crafty. Luckily, I am going to show you how to make an exhaust extension for your portable generator for under $20.

1. Find the Diameter of Your Generator’s Exhaust

To ensure that you are going to have a secure connection from your exhaust extension to your exhaust, you will need to measure the diameter of the portable generator’s exhaust.

You can use a ruler or tape measure to measure across the exhaust tip and add about ¼” to ensure a slip fit from your extension to fit over.

You will secure it with a clamp later.

2. Determine the Length of Extension You Will Need

In order to properly extend your exhaust to a more ventilated area, you will need to determine how long your extension must be.

While this may differ from time to time, you will want to figure out the longest length you could need and buy accordingly.

You can find extension material in lengths of 6 feet up to 50 feet to fit your specific needs.

3. Find Exhaust Flex Tubing to Fit Your Dimensions

For your portable generator’s exhaust, you will want “flex tube.”

Flex tube is metal tubing made to be flexible for easy routing.

You will need to find a flex tube that fits your needs for fitting over the exhaust pipe and reaching to a vented area.

4. Get the Correct Size Clamp to Secure the Flex Pipe

To properly secure the flex pipe to the exhaust, you are going to need a pipe clamp that is made to fit your diameter of piping.

Pipe clamps can be found in all diameters to suit your application.

Most require a simple socket to tighten, so be sure to have one on hand.

Hose clamps can be used if your pipe allows it, but a pipe clamp will be your best bet with flex tubing.

5. Secure the Flex Pipe to the Exhaust Pipe

Now that you have your flex pipe and clamp, you can place the clamp onto the flex pipe and the flex pipe over the exhaust pipe.

Tighten the clamp down firmly to make a leak-free connection, but be sure not to damage the exhaust pipe.

You should be able to move the pipe around easily without the clamp moving. If it becomes loose, reposition and tighten it again.

6. Route the Flex Pipe to a Well-Ventilated Area

Now that your portable generator’s exhaust extension is installed, you can route the extension to a well-vented area.

This can be outside of a window, under a garage, or any other area that allows you to position your extension to properly vent your exhaust.

You will want to avoid letting your pipe make its way back into your area, so securing it will also help make sure it stays in place and exhaust fumes are not entering your workspace.

7. Disassembling Your Exhaust Extension

When you are finished using your generator, you are going to want to properly disassemble your exhaust extension for proper storage to prevent damage.

Leaving your extension on your generator will not only make storage difficult, but it will also increase the chances of damaging your newly built extension.

Unbolt the exhaust extension at the generator exhaust pipe and properly store your extension with your generator or generator accessories.

Can an Extended Exhaust Make a Generator Quieter?

It’s no secret that a portable generator makes a lot of noise; most industry standard models are in the 70-80db range. While at a jobsite or out in the open this may not be a big deal, but in a neighborhood, the loud noise can be a nuisance to your neighbors.

Not to mention, in a shop or garage, the sound could be magnified, making it louder than usual.

There are many ways to help silence the exhaust, including adding a muffler, adding a quiet box, and a few other MacGyver-style ideas! I will touch a bit on this in another article.

Key Take-Aways & Wrapping it up

  • Always measure out your needed parts to ensure a tight-fitting connection
  • Buy high-quality, exhaust-specific parts for added safety and longevity
  • Make sure your exhaust extension is tightened properly to prevent leaks
  • Make sure your exhaust extension is properly routed to a well-vented area

The importance of routing your exhaust is vital to keep you and others safe when operating your generator in close quarters.

This also allows you to bring in your generator during bad weather, such as a rainstorm or snowstorm that could potentially damage your generator (see this post about rain covers).

Always make sure you have a very tight connection and that your exhaust is being vented to a well-vented area.

So there you have it, 7 easy steps to extend your portable generator’s exhaust for less than $20.

Depending on your application, pricing may be slightly higher (or, hopefully, a little less)!

Ensure you are buying high-quality parts that are made for exhaust circulation to keep you and your generator safe.

I want to hear from you! Have you had to build an exhaust extension for your portable generator?

What other situations have required you to extend your generator’s exhaust? is an independent review business. I am not affiliated with any manufacturers and do not accept paid reviews. When you buy through my links, I may earn a commission which helps me purchase more generators for testing. - Scott Krager


  1. I’m not sure which part to measure. I have a Firman 8k dual exhaust What size diameter pipe do I want?

  2. I have an RV which i want to build the chassis of a suitcase generator into the side of the RV in an enclosed ventilated box, and because the muffler runs pretty cool, route the exhaust gas outside the box to the main muffler from the RV engine using high temp silicone hose. Any thought’s?

    1. Hi John! That might be a good idea, I would seek advice from a RV or auto mechanic 🙂


  4. can’t find a 1 1/4″ ID flex pipe, at least 8′ long. Found this in 25′ lengths ! But the cost was too high. ($60 +). Need it for generator. $20 is just wishful thinking….

  5. I have a Honda EU3000is portable generator and the way the muffler is made, I wasn’t able to add an extension pipe. I’m interested in either the Generac XT8000EFI or Honda EB 10000W, but I’m not sure if the Honda will take an extension. The Generac looks like it would be very easy however.

    Would doing this allow me to put the generator in a shed and run the exhaust outside?

  6. I am unable to find any flex tube in 2 1/4″ diameter.
    My camping tent attaches to the open hatch back door of my hybrid 2017 Toyota Prius. The Prius AC/HEATER system turns on/off during night as required (thermostatic controlled). When the battery runs down (approx every 2 hrs) the gas engine automatically starts up & runs about 5 to 10 minutes to recharge the battery. I need to redirect the exhaust from under the car to an area 4-6 ft away.
    Exhaust pipe diameter measures 2 1/8″ (obviously it is actually a metric measurement- a smidge less than 2 1/8″)

  7. I have the Craftsman generator M# 580.326311 and I was wondering if there is a adapter that would work on the square muffler so that I could run the exhaust outside , or would I have to take it off to install a flex pipe ?

  8. I have a Westinghouse WGEN7500 watt portable generator. I would like to simply extent the exhaust pipe out the side of the shed. Has anyone thought of using simple radiator hose? Does anyone know what temp a radiator hose would burn? or how hot the exhaust pipe gets? Thanks all.

  9. How do I extend the exhaust out on a pulsar 12000b portable gen set
    to allow the exaust to go out my shed?
    Thank you.

  10. I need to extend the exhaust pipe on my Onan Generator since it does not extend to my bumper. The present pipe is 1 3/8. Should I just get a 1 1/2 “ pipe? Thanks

  11. Hi Matt,
    I saw no mention of spark arrested removal. I believe there would be, or could be a problem by leaving it in and using an extension. It’s a fire prevented only, correct?
    Nice website, thanks for the tips.

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