Can You Run Flex Duct Vertically?

Can You Run Flex Duct Vertically

Can You Run Flex Duct Vertically?

Flexible ducting, also known as flex duct, is a type of ducting pipe that can be bent at different angles. There are a wide range of flex ducts available on the market: from rectangular PVC, and metal, to aluminium and vacuum hoses.

In this blog article, we will discuss the question ‘can you run flex duct vertically?’, which we hope you find useful.

What is a flex duct?

Flexible ducting is a bendy type of ducting. It is made of a round wire coil, usually covered in a bendable but very durable polymer (plastic).

Whereas, metal ducting is made of metal sheets, formed into rigid, rectangular and round tubes of varying sizes. Metal ducting is boxy, while flexible ducting is cylindrical.

Available in different sizes, lengths and materials, flexible ducting is ideal for short duct runs and temporary ducting systems.

Because it is lighter and more versatile than rigid ducting, flexible ducting is easier and quicker to install. It is also easier to make adjustments to flexible ducting after it has been installed.

In addition, flex duct can withstand high pressure levels, which is why they can be used for things like cooker hoods, car exhaust ducting, vacuum hoses and welding.

Usually, flexible ducting is cheaper than metal ducting, which takes more money and time to purchase, install and seal.

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Can You Run Flex Duct Vertically
Can You Run Flex Duct Vertically

How far can you run flex duct?

It is best practice to keep your flexible ducting short, at the manufacturer’s recommended intervals: usually at no more than 4 feet. Use only what you need, because if your ducting is overly long, then it will take longer for the air to travel through the system.

If your flexible ducting is too  long, then you may be able to cut it, using a table saw or hacksaw.

Do not exceed the maximum spacing requirements when you are installing your flexible ducting between supports. The space supports should be no more than 4 feet apart, and they should not constrict the insulation, as this can cause cold spots and condensation which eventually leads to mould growth.

During installation, flexible ducts need to have the inner liner pulled tight, to prevent the friction rate jumping too much and impacting on the air flow.

Avoid running your flexible ducting across kinks and sharp corners exceeding 90-degree turns.

Also, do not leave your flexible ducts in a compressed state, as it may lose its circular shape.

Additionally, you should not install flexible ducting near hot equipment that is above the recommended temperature for your flex duct; that means taking care when it comes to appliances such as furnaces, boilers and steam pipes.

By the same token, avoid installing your ducts in direct sunlight or near an ultraviolet (UV) light source, as these can degrade some duct materials.

It is also recommended that your flex ducts should sag no more than half an inch per foot of length between supports. What’s more, the straps that hold up the flex duct should be no less than 1.5″ wide.

Remember to hold your flexible ducts in place with tie wraps at all connectors.

Can you run flex duct vertically?

So, can you run flex duct vertically? Yes, it is possible to run flexible ducting vertically. You should read the manufacturer’s guide to see if your chosen flex ducts are able to run vertically.

The flex ducts should be stabilised with support straps at a maximum of 6 feet.

However, the flex ducts cannot be used vertically in air duct systems that are more than 2 stories high.

Can you cut plastic ducting?

Yes, if choosing to install your plastic ducting yourself, you can cut the ducting.

If your pipe or flat channel needs to be cut, after measuring and marking with a pencil, use a table saw (mitre saw) to get a straight and neat cut through your PVC pipe. If you do not have access to a table saw, a hacksaw can be used.

Ensure when using a hacksaw you keep the cut as straight as possible. Using a pipe vice and a smooth controlled action on a handsaw will help you to achieve this.

If your cut is crooked, you will have a much harder time correctly joining lengths of pipe to each other or connecting parts. You will also find that pressure loss is a real issue.

Once you have your cut pipe, rub-down the point at which you made the cut with coarse sandpaper to give yourself a smooth surface to work with. Much like with cutting crookedly, if your cut is not clean, you risk pressure loss and connection issues.

Can You Run Flex Duct Vertically
Can You Run Flex Duct Vertically

Where can I buy flex duct?

Here at I-Sells, we offer various Flexible Ducting options to suit your needs.

We recommend our Aluminium Flexible Ducting – 10M – 100mm, which is a quality, uninsulated, puncture-resistant ducting. This product is suitable for use in high, medium and low pressure air conditioning and ventilation systems.

This is a ‘sag free’ yet ultra flexible duct, with excellent friction loss characteristics and reduced levels of noise generation.

This range of hoses can be supplied in diameters from 80mm to 500mm – Click here to view the full range of Aluminium Flexible Ducting.

Can You Run Flex Duct Vertically
Can You Run Flex Duct Vertically

Shop our Aluminium Flexible Ducting – 10M – 100mm here.

One of our budget-friendly options is the Kair Aluminium Flexible Hose 100mm – 4 inch – 10 Metre Length.

Lightweight and flexible, this hose can be used as a part of a long ductwork run for a variety of purposes, including whole-house ventilation, passive stack vent, air conditioning, positive pressure ventilators, HVAC, and Heat Recovery Systems.

This versatile product is ideal for use with extractor fans, cooling systems, cooker hoods, and tumble dryers.

Made in the UK, this is a genuine Kair Product and it is covered by the Kair 100% Satisfaction Guarantee.

Shop the Kair Aluminium Flexible Hose 100mm – 4 inch – 10 Metre Length here.

Can You Run Flex Duct Vertically
Can You Run Flex Duct Vertically

Not sure what type of flexible ducting you need?

Contact us with your enquiry, and our friendly team will be happy to advise you.

How much can you bend flex duct?

Your flexible ducts can be bent, but you should not bend them excessively. Every sharp corner, turn and kink will compromise the HVAC system, as it will reduce the airflow and create more friction inside.

Is flex duct better than rigid duct?

Flexible ducting and rigid ducting each bring their own strengths. One of them may be more suitable than the other for your requirements.

  • Flex ducting is easier and quicker to install
  • Flex ducting can fit better in awkward, tight spaces
  • Flex ducting is not as durable as rigid ducting
  • Flex ducting tends to be cheaper than rigid ducting

Does flex duct reduce noise?

The Heating, Ventilation and Air Conditioning (HVAC) unit in your home will make noise as it runs.

So, flexible ducting in a HVAC unit does the reduce noise generated from the machine and the air flow.

About I-Sells

Established in 2005, I-Sells is the UK’s largest ducting and ventilation supplier.

I-Sells was co-founded by Ingrid Sells, who was aware as a youngster that her surname would suit the name of a shop one day!​​

With a vast range of products available online, I-Sells is a one-stop shop for all ventilation supplies. A family-run business, the company will help you find the parts you need- whether it is a commercial project or a small DIY project.​

From plastic ducting and metal ducting, to extract fans, flexible hoses and mould control tools, there are thousands of useful products available. The product range is constantly increasing to meet customers’ requirements and expectations.​

We stock and offer next day delivery on thousands of our products, with free delivery on any order over £100.

The expert team at I-Sells can provide expert advice about the products and how they can be used to solve your problems or improve your home.​

Most products help solve damp and condensation-related problems. I-Sells also has one of the largest selections of plastic and metal ducting available online.​

In most cases, I-Sells can also manufacture a custom-dimension product for you- contact the company for more information.​

To find out more about I-Sells, visit the company website here, or email​ Alternatively, call us on 020 8463 9696.

To visit us at our showroom:


Monday – Friday: 8:00 am to 5:30 pm

Saturday: 9:00 am to 12:00 pm

Sunday: Closed

15 St John’s Parade

Sidcup, Kent

DA14 6ES, United Kingdom

Keep up with I-Sells on Facebook, Twitter, Instagram and YouTube here.

We hope we have answered the question ‘can you run flex duct vertically?’

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