What is that fan on the toilet cistern for?

August 13, 2006 12:15 AM

My friend has moved into a flat, the building being probably 30 years old or so, and on top of the fairly old toilet cistern is a small electric fan unit. We simple cannot work out what it's meant for.

The fan is enclosed in a square housing which is firmly attached to the top of the the cistern lid. There is no ventilation in the top or sides of the cistern, and only a small outlet on the side of the fan housing.

A hole opens between the housing and the lid, so that air is drawn from inside the cistern and sent out the side of the fan housing. The whole unit plugs into a mains power point right next to the toilet.

It obviously serves SOME purpose, but we can't work it out. I thought it might be meant to disperse some sort of deodorant, but there seems to be nowhere to put it. I can do a drawing of it if my description is not clear.

What on earth is it for?

posted by tomble to Home & Garden (9 answers total)

Best answer: There are fan systems for toilets which vent smells from the toilet pan via the overflow pipe connecting the cistern to the pan. This fan seems like it would do something similar but in case for that to make sense, it would have to vent the air outside the room somehow or perhaps filter them somehow.
Or perhaps it's a extremely poorly thought-out extraction system to prevent condensation on the cistern.
posted by insomnus at 1:01 AM on August 13, 2006

Response by poster: Insomnus - that may be what it's for. The toilet itself has no vents, I'll see if I can find an external venting port which has been disconnected from the unit.
posted by tomble at 1:33 AM on August 13, 2006

Response by poster: Oh, by toilet I mean the room which houses the unit. It's kind of in the middle of the house with nary a window or ventilation in sight.
posted by tomble at 1:42 AM on August 13, 2006

Could it be a primitive humidifier?
posted by Kirth Gerson at 4:48 AM on August 13, 2006

I am thinking it is an attempt to keep the WC tank from sweating.A picture may help me give a better asessment.

Is it at least on a GFI circuit for safety?
posted by plumberonkarst at 4:59 AM on August 13, 2006

But, as I said (or at least tried to) it wouldn't help at all in reducing condensation. To do that, the ventilation system would have to remove moisture from the room and moving presumably moist air out of the cistern would not help at all.
posted by insomnus at 9:22 AM on August 13, 2006

I think it's there to keep the toilet from swallowing too much air when you flush it.

The glug-glug noises you hear at the end of a flush are air being sucked down into the pipes after the water, and that air has to get back out of the pipes somewhere or it could back up the whole system. Most plumbing arrangements have a vent pipe for this, and so might this one, but this fan would at least minimize the air being sucked into the pipes by matching or overmatching the suction of the water.
posted by jamjam at 11:43 AM on August 13, 2006

Is it possible it's just there for the noise? I've seen bathrooms that didn't have an actual fan, but had a device that made a fan-like noise when you turned on the light. The purpose, of course, would be to avoid embarassment caused by others hearing the sounds of one answering nature's call.
posted by cerebus19 at 2:19 PM on August 13, 2006

Response by poster: Insomnus has it, it's for ventilation via a small port we found in the wall. What it's missing is a tube to move the air out of the bathroom.
posted by tomble at 8:06 PM on August 15, 2006