bathroom extractor fan

24 Jun 2014
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United Kingdom

Not sure if this is quite the right place for this query, but here goes.

I have a second (top) floor flat with no extractor fans in kitchen or bathroom. There's not enough space on the external wall of the bathroom to put an extractor fan on that side (i.e. to get it far enough away from the bath and shower), so I think the fan inlet will have to go in the ceiling.

My problem is where to put the fan outlet. I have access to the loft space, but would prefer to avoid doing any work on the roof (expensive, since that wouldn't be a DIY job for me!). This leaves one possibility - the waste vent pipe goes up through the airing cupboard next to the bathroom and into the loft space and then out of the roof.

Is it legal/sane/feasible to connect the outlet of an extractor fan to the waste vent pipe?

Any advice or other ideas appreciated!

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Is it legal/sane/feasible to connect the outlet of an extractor fan to the waste vent pipe?
no, no, and no,

does you roof have no gable walls or eaves?


Yes, there is a gable wall, but at the other end from the bathroom (about 8m). There are soffit boards, and I gather that one of the standard approaches is to have the outlet there. However, I was hoping to avoid having to got up a ladder that long to do it...

Is this the kind of thing that you had in mind?


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Thank you to everyone who has replied to this. I'll look into using one of the inline fans with outlet in the soffits.

I like that Soler & Palau, but it might suck the windows in.
Or pin animals and small children to the intake grille....

I wonder if they do one with variable speed.
The one I linked to has 2 speeds.

Contact the manufacturer - they are responsive.

at 250m³/hr and 100mm ducting, this one would suit me.[/QUOTE]
Remember that by the time you adjust for static pressure, losses at the intake, losses in the ducting and losses at the output vent you never get anything like the published performance out of a fan, which is why people who buy tiddlers because they appear to do the recommended air-changes-per-hour (which is probably inadequate anyway) get such dismal results.

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