Extractor fan condensation

[Lickdan]

Fitted an extractor fan in may this year and only just painted the bathroom have just noticed some streaking down bottom of wall in centre of fan so think the tube I fitted must be not falling adequately. Need to have a look but wondering if
I could lag internally with self adhesive neoprene. Run on timer is only a few minutes and can’t see it being rain as sure I would have picked up on it before. Fan has a lip of about a inch that inserts into tube, so could be coming below where the fan fits into tube.

 

[Ivor Windybottom]

If you insulate internally then you'll reduce its diameter, reducing its effectiveness. You'll also create a rough inner surface that will gather dust and grot.

I don't see an issue in the photos. If the duct falls outwards then there's nothing to worry about. If not then take it out and re-fit it.

 

[Murdochcat]

Increase the run on timer and if the fan has a back draft option , remove it

 

[jj4091]

In my opinion you have the wrong type of external cover. You need one of these https://www.screwfix.com/p/manrose-cowl-vent-white-100mm-x-100mm/16195?tc=BA7 rain and wind conditions have to be perfect to blow back through the fan so you may not have had those conditions in the recent past.

 

[foxhole]

You don’t appear to have fitted external back draft shutters which would prevent rain blowing in .
Agree with JJ above .