I fitted a Manrose 100mm Standard Mixed Flow Fan in the attic 3 years ago, to replace a failing fan there. Of late we've been getting an unusually high level of condensation in the bathroom after showering, and I've been trying to determine the cause. There was a fair bit of gunk build-up on the grill above the shower, and also on the grill in the soffit outside, and I've cleaned them both and hoovered out the insides of the duct as much as possible. But I was wondering if the fan itself might be pulling less air through, and might need some kind of maintenance. Or is it a case with these fans that they tend to either work fine or fail completely?
Do in-line extractor fans require maintenance?
- Thread starter Johnny2R
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As a general rule of thumb, with the fan on, hold a piece of toilet roll to the inside vent, does the suction of the fan keep the toilet roll stuck to the vent? If so then the fan is likely sucking enough air in from the bathroom.
However, as you have dust buildup on the external vent one could conclude that the blades of the fan may well have a similar build up which I’d suggest you try and get to to clean off.
However, as you have dust buildup on the external vent one could conclude that the blades of the fan may well have a similar build up which I’d suggest you try and get to to clean off.
Can you access the vent pipe ? If so see if it "dips" and allows a build up of water - which will restrict the air flow
Or have you had a new floor covering under the door that has reduced the airflow into the room?
Or have you had a new floor covering under the door that has reduced the airflow into the room?
Interesting thought. New carpeting in hallway, some months back, but probably not put to the test, as it were, until recent colder weather. I'll have a look. We do always keep a small window slightly open in the bathroom, though.
There's no build-up of water in the pipe.
Yes, the piece of toilet paper stays nicely in place. I actually haven't tested this since I did my last bit of cleaning earlier and it may well be now that the flow is as good as it gets, but I was just curious about the possibility of the fan itself underperforming. If it's simply a case of cleaning the fan vanes, that should be easy enough, after removing the inlet duct.
Keeping the window open in the colder months just means you’ll be drawing moist damp air into the room
Try shutting the window
Ah, OK, I thought I needed to have some airflow, air coming into the room to replace the air the extractor fan is pulling out. But you're suggesting that should be coming from inside the house? Having looked at the door area, I don't think the new carpet should be restricting airflow under the bathroom door, there's still a decent gap.
Next time you have a shower, open the door a little and see if that helps the flow into the room -
How long does the over run go on for?
It's manual, a fan we switch on and off as necessary.
If you have a steamy bathroom, it’ll take a minimum of 10 minutes to clear it, if not more
Next time you use it, leave it on for longer
So where does the air that the fan exhausts get replaced from?
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Nearly no properties in this country are built with anything like a decent level of air tightness. There will likely be square metres worth of gaps, cracks, holes and splits throughout the structure, around windows, doors, floor edges and between floorboards, in the loft, around service entry points.. You name it; point a camera in any direction and I bet it'll catch at least 3 potential sources
Definitely much less condensation in the bathroom now, thanks! Keeping the windows closed and leaving the door slightly ajar. A good clean out of the grills at both ends and the duct itself has helped a great deal. Am I right in thinking that it will be beneficial if the duct (in the very cold loft space) is insulated? I am assuming that it will benefit flow if there's no condensation taking place in the duct itself.
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Definitely a good idea, you want to give it the best chance of getting outside before it condenses, otherwise it'll just sit in the duct until it freezes/evaporates again
So the best course of action is to shorten the door to the bathroom.
Putting a thin layer of loft insulation over the vent pipe should sort the condensation
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