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Plastic Ducting Guide

Plastic ducting

What is plastic ducting?

Plastic ducting is usually made from PVC. It is a durable, lightweight material. If you are installing an extractor fan or passive ventilation system to control condensation or mould growth, you may choose plastic ducting to vent to the exterior of your property.

Plastic ducting is typically used as ventilation within domestic properties, principally within student flats and modernisations. It is preferred because of its lightness, its airtight properties & durability.

By contrast, spiral metal ducting is often used within commercial & industrial properties.

Plastic ducting has a number of advantages over other types if ducting (such as metal spiral ducting) including:

  • It is lightweight
  • It’s easy to install
  • It’s smooth on the inside, making for efficient installations
  • It is easy to cut
  • It doesn’t corrode
  • It can be insulated

What is round plastic ducting?

Round plastic ducting has a circular cross-section. This means that it has the greatest airflow performance. Round ducting doesn’t have corners, either, increasing airflow. Its shape can make it more difficult to conceal and install than rectangular ducting & so, if that is an issue for where it is to be installed, it may not be the best choice.

It is recommended for most applications & is used for ventilation systems, HVAC systems, bathroom, toilet and utility room extract fan venting & where high levels of extraction are required.

What is rectangular plastic ducting?

Rectangular plastic ducting is useful in short, simple runs. It takes up less height than round ducting & is preferred when working with restricted or tighter space. It is particularly appropriate for most household, commercial and light industrial applications which require lower extraction rates such as bathrooms, toilets and utility rooms. It is designed to be airtight and easy to fit to a range of different fittings such as bends, connectors, reducers, transformers and grilles. It is important to keep the number of bends in these systems to a minimum to increase airflow.

What’s the difference between round ducting & rectangular plastic ducting?

The largest difference between round and flat plastic ducting is the free area or space within the duct. Generally speaking, the greater the free area, the greater the airflow & so the greater the level of ventilation.

Here’s an example:

  • 100mm round plastic ducting may have a free area of 7,855mm².
  • 100mm equivalent rectangular ducting (110x54mm) would have have a free area of 5,424mm²

As you can see, round ducting has a much larger free area (around 45%) than rectangular ducting & is therefore much more efficient.

What are the advantages & disadvantages of round ducting?

Round ducting has a number of advantages over rectangular ducting including:

  • Lower levels of friction
  • More efficient airflow
  • Simplicity of connection
  • Speed of installation
  • Better ability to handle higher pressure
  • Lower cost of installation
  • Lower noise levels

The disadvantages are:

  • The space requirements are higher
  • Not as efficient for low-pressure systems
  • Difficult to connect fan coils to the main duct

What are the advantages & disadvantages of rectangular plastic ducting?

Rectangular ducting has a few advantages over round ducting:

  • Less space required
  • Easy to connect to fan coils
  • Better for low-pressure systems
  • Easy to flush fit and conceal

The disadvantages are:

  • Less efficient airflow
  • Higher noise levels
  • Higher installation costs

How do I cut plastic ducting?

The simplest way to cut plastic ducting is to mark where you need to cut with a pencil & use a mitre saw (although a hacksaw can be used if you are able to make a straight cut). It is advisable to sand the end too, so as to avoid a loss of pressure. Making a straight cut will pay dividends when it comes time to joining pipes together as it will be easier to connect the parts & you will be less likely to lose pressure.

How do I join plastic ducting?

Plastic ducting pipes are female & so it is easy to fit male connecting parts. By firmly pressing the parts together, the chances of pressure loss are minimised. Once they are pressed together, sealing them is simple with ducting sealing tape.

How to seal plastic ducting

There are a number of ways to seal plastic ducting including the use of ducting sealant & sealing tape.

If a round or rectangular rigid duct system needs to be permanently sealed, this is best done using ducting sealant which can provide an airtight seal. Ideally, the sealant would have an acrylic polymer base so as to minimise shrinkage & would be solvent free so that it does not attack any adjacent surfaces. Greater strength can be given to a joint with the addition of sealing tape.

Sealing tape can be used to maintain a seamless surface & to retain the thermal integrity of a duct system. Sealing tape can be used when a semi-permanent seal is required (ie when making a rectangular flexible hose joint).

The best way to seal plastic ducting us by using sealing tape.

Where can I buy plastic ducting?

We sell a wide range of plastic ducting, both round & rectangular.

Click here for rectangular plastic ducting

Click here for round plastic ducting

Please feel free to call, email or chat with us online to discuss whether plastic ducting would be correct for your installation. If you have questions about the technical data or installation of rectangular plastic ducting, then as experienced suppliers of rectangular ducting, we are here to help.