Water collecting in duct pipe from extractor fan in bathroom

22 Aug 2019
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United Kingdom
Hi all,

I discovered that water was collecting in the duct piping from the bathroom extractor fan to the roof.

I thought a temporary bodge would be to pierce it a couple of times and bleed the water out. (Hence the duct tape!) and to insulate it with some old duvet covers.

Obviously not a long term solution, and the water is still collecting. (Its been a very cold winter so the water has condensed faster in the pipe.)


Its probably about 5 meters from the extractor fan to where it exits the roof. And the exit about the fan is perhaps not even a metre.

What should I do?

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1) fit rigid duct, which is straight so does not sag into loops that hold water. Go straight up from the fan, then run the rest not quite horizontally, but tilting slightly down to the outside so any condensation runs out

2) wrap the duct in loft insulation so it is warmer and not prone to condensation

3) run the fan for longer, starting as soon as you go into the bathroom and before you turn on the shower, and running on until the room is dry. This can usually be accomplished by wiring the fan to the light switch, with a run-on timer

4) you might need a more powerful fan. Show us the one you have.
Thanks guys. Ill take a photo of the fan when I next go round there (hopefully today)

Im looking at condensation traps, but have nowehere for the overflow pipe to go. (Im not comfortable drilling holes by the roof line).

So the hard duct should look like the below?

I reckon the vertical bit of the pipe would need to be 1 metre. Ill measure when I next go over.

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Bends and excess ducting will reduce the airflow.
If the fan is one of the poxy token gestures that are fitted, you will have problems.
What is the termination outside ?
does your roof not have a gap at the eaves? where the roof is ventilated?
I will have a closer inspection of the situation (gaps at the eaves etc...).
Thanks so much for your fast/helpful replies!
If you run pipe vertically from the fan you would need a condensation trap. Good idea to run the fan longer to clear condensation in bathroom and dry out the pipe.
Heres the fan. Hardly looks like something Elon Musk would have in his bathroom! :LOL:


I can see daylight by the eves, so yes, running the pipe and/or duct at the roofline looks possible.
What sort of exhaust vent would you have at eaves or would you fit sofit vent?
You could poke the duct through the gap if it is big enough

As you have a loft duct you could have a ducted inline fan up there, three or four times the power, preferably a timer model

For example a very good make, though rather expensive

There are also cheaper brands

No doubt many of them are quite good, but I have not been impressed by Manrose in the past.
You have to be careful you don't get moist air from exhaust getting back in loft, that can certainly happen with soffit vents.
For a budget solution, do you think leaving the flexi duct as it is, but add the condensor trap and run the overflow pip out of the eaves?
Ive just fixed the issue. It is just a temporary fix (luckily we're going into summer so I wont need to worry about it for a few months). Ultimately I will do a proper job. But for now I just bled the water out (most of the length of the duct was full of water!!); wrapped duct tape around the bits I bled; and raised the duct up a bit.


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