Insulation

Extract fan dripping water

Warning Do not attempt any electrical or gas work yourself. Always use a qualified, MCS-certified, or Gas Safe registered professional for repairs.

What you’re seeing (symptoms)

Water is dripping from the centre of your ceiling-mounted extract fan, especially after a shower or when it’s very cold outside. You may see water stains on the ceiling around the fan or a “gurgling” noise when the fan is running.

What’s normal vs not normal

Normal:

A small amount of steam visible at the outside vent.
The fan being slightly louder in winter as it pulls in denser, cold air.

Not normal:

Actual liquid water dripping onto the floor or into the fan’s electrical components.
Black mould forming on the fan’s plastic grill.
Water “spurting” out when the fan first starts up.

Likely causes (ranked)

Uninsulated ducting: Warm, moist air from your bathroom hits the cold section of the ducting in your loft. The moisture turns into water (condensation) and runs back down the pipe into the fan.
Sagging ducting: The flexible duct pipe in the loft has “sags” where water can pool. When enough water builds up, it flows back to the fan.
Missing backdraught shutter: Cold air is blowing into the duct from the outside, cooling the pipe and causing condensation when the fan isn’t even on.
Poor termination: The duct doesn’t go all the way to an outside vent and is instead just venting into the loft space.
Fan speed too low: The fan isn’t strong enough to push the moist air all the way to the outside before it cools and condenses.

Quick checks you can do safely

Inspect the loft: Go into the loft (stay on the joists) and find the flexible pipe leading from the fan to the outside.
Check for insulation: Is the pipe wrapped in a silver or white “jacket” of insulation? If it’s just bare plastic, this is your problem.
Straighten the pipe: Ensure the duct pipe runs as straight as possible to the outside vent with no U-bends where water can collect.
Check the outside vent: Ensure the louvres on the outside wall or roof are not blocked or stuck shut.

When to call an installer

Immediately if water has entered the electrical part of the fan and it’s buzzing or not working.
If you need to install a new, insulated duct or a “condensation trap” (a small plastic collector with a drain).
If you need a roof vent installed to properly terminate the extract duct.

Questions to ask your installer

“Can you replace the uninsulated duct with a pre-insulated flexible duct?”
“Does the fan have a built-in backdraught shutter to prevent cold air entry?”
“Would a condensation trap prevent water from reaching the fan unit?”

FAQs

How do I insulate the pipe? You can buy pre-insulated ducting (the easiest way) or wrap your existing pipe in a “duct insulation wrap” available at most DIY stores. Why does it only happen in winter? In summer, your loft is warm, so the ducting stays warm. In winter, the loft is freezing. When the 40°C steam from your shower hits a 0°C plastic pipe, it turns into water instantly. Is the water dangerous? Yes, if it gets into the fan’s motor or your house’s electrical circuit. If it’s dripping from the fan, you should turn the fan off at the isolator switch until it’s fixed. What is a condensation trap? It’s a small plastic fitting you put in the vertical section of the duct. It catches any water running back down and allows it to be piped away safely, usually to a waste pipe or outside. Will a more powerful fan help? Yes, sometimes. A “centrifugal” or “inline” fan can push the moist air out much faster than a standard wall fan, giving it less time to condense.\n

Written by NetZeroNow | Last updated on 2026-03-02

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