Bathroom Extractor Fan Issues

1 Feb 2017
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United Kingdom

Looking for some advice. Having an issue with bathroom extractor fan in a 2 year old house. After noticing some staining on the roof around the fan we had a look in the loft and found the ducting full of water. The duct lies horizontally for about 2 metres then vertically for about 2.5. Wondering if making the duct mostly vertical or at a slope will prevent this from happening again.

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Yes that will definitely help, is the ducting the plastic flexi corrugated type pipe that you see on tumble dryers?

These are a 'mare for filling with water if laid flat as the ridges hold water as you've found.
Usually find lower powered fans are more prone to storing water since they don’t clear condensing water from vent.
Also fan needs to run on after use and/ or every time room is used which helps prevent a build up of condensation.
Have not had any problems with my high powered shower room fan despite a long run.
Insulating the vent can reduce condensation but is not easy and maybe not be worth the hassle .
It is possible to put inline condensation trap on the vent and run overflow pipe outside from this .
One example , would need to be positioned at lowest point of vent ducting and sealed effectively to ducting to avoid leaks .
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Leak has returned, but this time it’s the fan itself that has filled with water! Ceiling above is also wet and some of the loft insulation around the fan. I haven’t been up above the ceiling to take a look but I guess this is because there are now no low points for water to collect in the duct, so it’s running back to the fan. As it’s the bottom casing of the fan that seems to fill up first (before the electrics are affected) I’m thinking of drilling a small hole in the casing and just putting a dish under it to catch the drips...
Are you sure it's not just rain getting in ?

It does vent through the roof after all....

I would be checking everything is properly sealed
Is the duct going vertically through the roof.

I ask as when my bathroom duct pipe was filling with water I found that it was:

- Where the pipe goes through the roof, the cold roof is touching the pipe.
- The cold roof made the inside of the pipe colder at this small section, than along rest of the pipe.
- So the bathroom Stream/Vapour was happily passing along the entire length of the loose pipe, and then condensing into droplets of water at this roof boundary point.
- Water then running back along pipe and leaking out (rotting the ceiling below).
(was not rain, I could see the water droplets at this cold point when I pulled off the duct).

1) I made the pipe as virtual as possible and fitted a "duct condensation collector".
This needs somewhere for the water to go so I fitted a pipe out through the roof eves.

2) If possible, re-route and Direct the pipe to go horizontally out through the eaves in the loft with a slight downhill inclination.


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