Brown liquid coming from bathroom extractor fan - any ideas?

[starfish4]

About a month ago my Mum had brown liquid dripping from her extractor fan, almost dark red. We checked in the loft as it vents up through the roof and could find no signs of a roof leak. There are pipes about 30cm to the side but with no condensation of sign of a leak. Unfortunately, she did have rats at the time and I half put it down to the fact that they could have been weeing near extractor fan. Pest control have confirmed rats are cleared, she mentioned she was worried and the chap had a look and said it was slightly damp over the extractor fan (he also confirmed he couldn't see a problem with the roof or pipework) - any ideas?

Also, who should we get in to check out, electrician as electrical, plumber to check out pipe and vent or builder.

Condensation, probably washing back with rust or dirt.

I gather there is a duct in the loft. This should be sloping so that condensation runs outside the house through the vent in the wall, not back towards the fan. Rigid duct is much cleaner and less prone to dirt and condensation that the flexible hose, but installers often like hose because it takes less effort.

The duct should be wrapped in loft insulation to protect it from the cold which causes condensation. Running the fan for longer will also dry it.

Some photos of the fan and duct and exit vent will help. If water is getting into the fan it will fail soon. You can get an electrician to fit a better one and improve the duct.

Thank you. There is a solid brown pipe that vents up through the roof - has been okay for many years, but obviously things do wear. If my Mum doesn't get it sorted soon, will post some photos after my next visit. Also, good to know who we should contact as a first port of call.

If you can borrow some binoculars, have a look at the roof vent. It is probably on the ridge of the roof, or a vent tile. If broken, loose or out of place, ask around for an established local roofer to replace it.