Preventing water entering extractor vent pipe

We have a bathroom fan which, for reasons known only to the contractors that did the work for the people before us, vents straight up out of the roof of our first floor bathroom.

As a result of this, because we’re located in a relatively exposed spot (halfway up the side of a hill) rainwater (presumably when driven by wind) has entered the extractor pipe, knackered the fan and caused the plaster to crumble around the fan fitting.

We recently had the bathroom re-done, and as part of those works, our bathroom fitter agreed to replace the bathroom fan and make good all the plaster etc.

Except – he didn’t do any of it. I’ve thrown my toys out of the pram, but he’s made it quite clear he’s not coming back to do it and has deducted the cost of doing so from our final account, so we’re no worse off.

The fan is a Greenwood centrifugual fan – his electricians said they’d never seen one like it (!) and didn’t know where to get one from. Google turns up Greenwood Airvac and various fans.

Anyway, I can probably get someone in to replace the fan, but what I want to do is prevent the water ingress problems happening again. I think it was probably this that meant the fitter didn’t want to do it.

The extractor flue is what I think is standard 100mm (possibly 110mm?) round ducting terminated by a rain hat – like this:

But it’s clearly not working. The flue extends probably 500 – 600mm from the pitched roof.

My thoughts are to reduce the susceptibility to rain ingress the pipe could be cut down so it’s more shielded by the building as it wouldn’t protrude so far from the roof. Repositioning the fan isn’t an option as the bathroom is now finished and I don’t fancy having someone with a core drill going through all the new tiling. Plus it would need someone on the roof to close off the existing vent.

Can anyone recommend a rain cowl that works well? Any other suggestions? Would introducing a bend into the pipe help (I presume not)?

Would it be possible to ditch the protruding flue and put in a tile vent? Something like –
https://www.screwfix.com/p/glidevale-universal-tile-ventilator-brown/1091T?kpid=1091T&ds_kid=92700058021678421&ds_rl=1249407&ds_rl=1241687&ds_rl=1245250&ds_rl=1245250&gclid=CjwKCAiAq8f-BRBtEiwAGr3DgaQFYUg7DOaFuLgqg-hlpIJqLisv7QBmfE5vy4OyZdXou_TuFVOhhhoCIwEQAvD_BwE&gclsrc=aw.ds

Are you sure it’s rain water getting in rather than condensation in the flue due to it’s length outside the roof in the cold?

Every chance it’s condensation as much as it is rain. Tile vents here for both showers and also kitchen extractor.

I have those mushroom caps on all the fan flues I have fitted with no issues with water ingress. Not that that is helpful to you

You could put a 180 degree bend into it which would make rain ingress impossible

You could put a 180 degree bend into it which would make rain ingress impossible

Don’t do this. It’s otherwise known as a ubend and all the condensation will build up here -fungus awaits.

Tile vents here successfully

Your going to need someone to do something on the roof so may as well enquire about the cost of a tile vent.

trailrat – I meant in the vertical pipe above the roof so no water trap so N shaped not U shaped

You can also get drainable water traps I believe but I have not had the need and in a short straight pipe maybe not fitable

Would it be possible to ditch the protruding flue and put in a tile vent?

Are you sure it’s rain water getting in rather than condensation in the flue due to it’s length outside the roof in the cold?

Nope, not sure at all. In fact, that may well make more sense. I just assumed (since it’s clearly water damaged) that it was rainwater, but condensation would also explain it.

The problem with works on the roof is that it’s pretty high, with no access from our property to the side of the house that has the vent on. I can clamber up through a Velux to put a new cap on, but I doubt anyone would do the works to put a new tile on without scaffolding, which massively increases the cost, and would need a neighbour’s permission to put up in their garden.

Hmm, we may need some other roofing work done in the new year (flat roof elsewhere needs recovering) so may be worth speaking to them about a tile vent at the same time.

It may be rain but it could also be the steam extracted from the shower condensing in the pipe as it rises through the pie to the exit. It will do this as the extraction pipe will get colder as it nears the exit.

Solution: Insulate the extraction pipe, reduce vertical runs, better fan.

It may also be rain getting blown in.

Is it a flexible duct up through the roof space? Our extractors vent at the eaves after running horizontally across the lagging. You’d still need someone to come and make good the tiles.

If there isn’t an inline flap vent to stop air moving through the pipe even when the fans off, then it could also be warm air from the house condensing in the vertical cold pipe.
Can also fit a condensate trap in the pipe run
All this can be done inside the loft.

This happened in our house; cold well
Insulated loft causes water to condense in the vent pipe as the water vapour from the shower rises through it. If it happens when it doesn’t rain every chance this is the reason. Solution insulate the vent pipe or do what we did replace then pipe with an insulated one.

As already mentioned above, probably condensation on the pipe.  We had that as well.  We just cut the pipe a lot shorter and all was well.  Insulating it will also help, you could easily lag it to just below the hat

Condensation caused this in a couple of our houses before. It wasn’t rain coming in.

My loft pipe is insulated and angled craftily to the eaves vent, draining condensation to the outdoors.

We had this problem in our old house,  but it was steam from the bathroom condensing & coming back down the duct, as well as the centrifugal fan that failed being replaced by a weak axial fan (by my father-in-law).

I got rid of the axial fan, replaced it with a new centrifugal fan and lagged the ducting in the loft which solved the problem completely.

Perhaps it is also rain,  but I’d be trying to reduce the chance of the vapour in the pipe condensing before taking the more difficult job of the roof interface,  which might not be a problem in the first place.

you might be surprised about lack of scaffolding. my old gaff had a roof where the nails were failing, so needed a couple of tiles replaced every year. I’d just ring a few people up until I found one who was happy to do it with a ladder, cash in hand, one weekend morning. 20 minutes work for them, an easy £100

From experience, I’d say that it’s due to condensation. Just put some insulation around the ducting. Certainly easier and cheaper to try before getting on the roof.

Hmm, thanks all but it’s not routed through any loft space – it’s essentially inner plaster/board, presumed cavity with insulation, and then roof – so I don’t think insulating the ducting is an option. I suppose we could get someone to rip out the inner wall to take a look, but I think that may be a bit extreme.

I think short term I will try and shorten the pipe – as a minimum, that might ease any condensation problems, and possibly replace the fan, and then in the new year get someone to take a look.