Bathroom Fan - condensation in pipe

[AndyPRK]

Hi

Noticed a damp patch on my en suite ceiling today.

Got up in the loft and thankfully not a tile off, just loads of water in the fan outlet pipe (built up over 5 years )

I don't use the shower in there.

There didn't seam to be any obvious problem with one point being lower.

How do I correctly route it to prevent this?

Checked the bathroom one and that was fine.

Thank you

 

[oldbutnotdead]

If there's water in the pipe it is sitting level. If you can, jack up the internal end so any water that does get in there (condensation, rainwater) goes back out. If you can, have a look at the external exit- has the louvre gone AWOL (or was one ever fitted)?

 

[AndyPRK]

The vent end is high up. It's in a tile on an Apex roof.

Think its condensation due to being cold outside and warm inside

 

[lt8480]

The pipe should continually rise - with the room side being the lowest and the external side the highest.

If you insulate/lag around the pipe this will help minimise the chance of condensation forming (as it will keep the pipe surface and the air warmer until the air goes out the building).

 

[AndyPRK]

Thank you. There is a kink at the top where I tied it to the beam. I guess water forms in this shelf and runs down.

 

[lt8480]

Also worth nothing that when the fan is not on some air will still rise through the pipe (albeit only a little amount and slowly). However, if you have a downward section air will "sit" in this section (a bit like water sits in a toilet u-bend) and consequently have more time to cool down than it does in the rest of the pipe (which will have a slow trickle of warmer air running through). This stagnant area of air is then more like to condense as it is cooling more and has little air movement (especially if the fan is infrequently used for long periods).

 

[foxhole]

For ensuites and bathrooms you need an efficient fan, standard fans don't shift the air rapidly enough to avoid condensation.
Ideally fan runs anytime the room is used which also promotes good ventilation and moves condensation in the vent.

 

[John D v2.0]

Insulate the duct, run it horizontally, use rigid duct, if you must go vertical then fit a condensation trap and drain off, make sure the fan has a run on after use

 

[AndyPRK]

For ensuites and bathrooms you need an efficient fan, standard fans don't shift the air rapidly enough to avoid condensation.
Ideally fan runs anytime the room is used which also promotes good ventilation and moves condensation in the vent.

I don't use the shower in there, so I know its caused by poor pipe route.

I painted the ceiling/walls this week, so I better get up there are remove the kink

 

[AndyPRK]

Checking my pipe, it has significant water in it again. I will try and post a pic of the run.

My (identical) fan in the bathroom is fine though, but it gets used

 

[clifford1]

Does the exit have blow-back flaps or just a fixed louvre?
In recent gales and rain I've found wind can drive rain almost anywhere. High at the apex of a roof would be a prime target for catching gusty wind.

 

[^woody^]

Just turn the fan on for a few minutes every five years.

 

[AndyPRK]

I don’t think it’s rain water from recent gusts.
I did notice a ceiling patch a few months ago.

There is an exit tile in the roof Apex.
Has a cap on it.

 

[AndyPRK]

 

[opps]

I thought those types of ducts could be fitted with a pipe similar to a toilet overflow pipe that allows condensation to drain off?

eg https://www.amazon.co.uk/Condensation-Recovery-Ducting-Extractor-Bathroom/dp/B00IORF1NW

Must admit, I have never used one through. I have only ever vented straight out through the wall.