A Complete Guide to Installing an Inline Extractor Fan in Your Bathroom

A Complete Guide to Installing an Inline Extractor Fan in Your Bathroom


Bathroom ventilation is crucial for maintaining air quality and preventing issues like mold and moisture buildup. One effective way to achieve this is by installing an inline extractor fan. In this guide, we'll walk you through the steps to install a 100mm/4" inline bathroom extractor fan with a timer, ensuring your bathroom remains fresh and moisture-free.

What You'll Need:

 Before you begin, gather the following materials:

  1. 100mm/4" inline bathroom extractor fan with timer
  2. PVC or aluminium flexible ducting
  3. Four ducting clips
  4. Internal air vent
  5. External grill

The Power of Inline Extractor Fans: Inline extractor fans are powerful devices capable of extracting 85-180 cubic meters of air per hour, depending on the model. They are designed to be installed remotely in the ceiling or loft above the bathroom, reducing noise and minimizing the risk of water damage. The plastic fixing bracket of the fan is attached to a suitable surface, secured to the ducting using ducting clips at each end.

Installation Process:

Ensure Correct Airflow: When installing the fan, make sure to check the direction of airflow, typically indicated by a sticker on the fan. Proper airflow direction is crucial for effective ventilation.

Timer Setting: The inline fan comes with a timer that can be set to a maximum of 20 minutes. This feature ensures that humid air continues to be extracted from the bathroom for a set time after the fan or light is switched off.

Internal Vent: Attach the internal vent to the internal extraction point in your bathroom, usually located above the power shower. Some internal vents even come with LED lights. Secure the internal vent to the end of the flexible ducting using ducting clips.

External Vent: Install the external vent at the extraction point where the ducting leads outside. This can be through a soffit or gable end wall. If the extraction point is through a vertical wall, use a gravity grille to prevent back-drafts from entering the fan through the ducting. For extraction points through a soffit, a fixed grille is more appropriate.

Optimal Fan Placement: Ideally, position the inline fan halfway between the internal and external extraction points. This helps minimize stress on the fan's motor and extends its lifespan. For optimal performance, keep the ducting length between 6-10 meters. The fan should be as close as possible to the external extraction point, as these fans are better at pulling air than pushing it. Ensure that the ducting is pulled as taut as possible during installation to minimize airflow resistance.


Installing an inline extractor fan in your bathroom is a smart investment in maintaining air quality and preventing moisture-related issues. By following the steps outlined in this guide, you can achieve effective bathroom ventilation and enjoy a fresh, mold-free environment. If you have any questions or need assistance with purchasing the necessary components, please don't hesitate to contact us at sales@crwltd.co.uk or call 0208 998 0033. You can find all the parts you need for your bathroom extractor fan kit on our website www.crwltd.co.uk.