Bathroom extractor fan dripping down wall

[Postik]

I have an Envirovent Silent 100 extractor fan in my main bathroom and en suite. In the winter both of them drip. The one in the en suite isn't a problem because it's fitted in the ceiling so drips on the toilet seat and can just be wiped up.

However, in the main bathroom the extractor is on the wall, and you end up with a big long drip mark all the way down the wall. I'm worried eventually this is going to stain the wall. It doesn't happen in the summer so is definitely condensation related. People sometimes say run the fan for longer, but this occurs when showing whilst the fan is running. I've also read to lag the pipe and I understand how to do this with a ceiling fan where the pipe goes into the loft, but I'm not sure this is possible or would make a difference with a fan that is fitted in the wall.

What could I try and do to fix it? It doesn't happen every single time, but if it's very cold out and three of us all have a shower one after another it's almost guaranteed to happen.

Thanks!

 

[jj4091]

Is there a cowl or backdraft flap on the outside. Does the pipe through the wall have a downward fall to the outside.

 

[Postik]

There's just a plastic air brick grill on the outside (no flap). Behind the fan inside the wall I can just about make out some kind of clear plastic flap which I think is part of the fan construction. I can't tell if the pipe has a downward fall, I'm assuming someone just drilled a hole and put the fan in - so I don't know if any adjustment to the pipe is possible?

 

[jj4091]

Is it possible that rain water could be blowing through the grill and fan and running down the wall, rather than condensation, there really should be a cowl on the outside to prevent that. You would need to remove the fan and check the fall with a spirit level in the pipe to determine if there is any fall and which direction it is in.

 

[Postik]

Thanks for your reply. It's definitely not rainwater, we've had some exceptionally heavy rain the last few months and it's never let water in. It only happens when showering and the room gets really steamy. You can almost predict when it will happen based on the temperature outside (i.e how cold it is) and how long you stay under the shower (i.e how steamy the room gets).

If the pipe is slightly sloped inwards does this mean it would need refitting? Is it worth trying to wrap insulation around the pipe or perhaps some foam on the inside of the cover?

 

[Alec_t]

I can just about make out some kind of clear plastic flap which I think is part of the fan construction.

That's the back-draft preventer. It does, however, restrict air-flow slightly in the forward direction and might act as a surface which collects condensation.

 

[Murdochcat]

Photos of the loft vent pipes would be useful

 

[Postik]

In the case of the main bathroom (which is the most problematic) the pipe doesn't go into the loft, it goes straight through the wall.

One thing I notice is that the fan on the wall is fitted on its side. Could this be preventing the back draft shutter from swinging closed and causing condensation? I guess the argument against this is that the one in the en suite also drips and that's fitted on the ceiling.

This is the fan that I have: https://www.envirovent.com/products/extractor-fans/silent-100/

And attached are some photos (not mine) showing the back of the fan and the back draft shutter

 

[Murdochcat]

edited

Prevailing wind direction ?

 

[JohnD]

i think it's lack of slope, and possibly lack of pipe. post some pics please, inside and out.

 

[Postik]

Hi there, please see some pics of the vent outside, and the fan inside (I've taken the cover off).

 

[JohnD]

After turning off the power, you can undo the fixing screws and remove the fan. There ought to be a plastic duct behind it, which ought to slope downwards to the outside so any condensation runs out. Your single airbrick is not usual. Normally a round duct, and an external vent, weather protected and with non-return flap is used (see link below for a cowl vent)

Also, IIRC that model should be fitted with the electrial connections at the top, so water will not run into them. You might be able to achieve that.

Cowl Vents | Ventilation | Screwfix

Buy Cowl Vents at Screwfix.com. A hooded vent. Prevents drafts. Suitable for flat or round ducting. Click and collect in hundreds of stores nationwide.

www.screwfix.com

 

[Postik]

Yes, unfortunately the fan is fitted on its side. If I remove the fan and the duct is sloping inwards rather than outwards, I'm assuming there won't be any easy way of fixing that?

 

[Murdochcat]

Those types of fan can normally fitted in any orientation

 

[JohnD]

Depends how the duct is fixed (if at all). I pack mine round with sand and cement mortar, sealing the external joint to keep weather ot, and supporting the duct with a slight slope, then finish with plaster on the inside. If the hole is oversize, you may be able to move the duct a bit.

Some people use expanding foam, or nothing.

You can use a core drill (which can be hired) to cut a neat hole, holding it with a slope as it cuts. But they are heavy and not safe to use on a ladder. Mine has a clutch that will release if it jams, I like to set it very low.