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Feb 3, 2021
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united kingdom
Member Type
DIY or Homeowner
Hi all,

We recently had a ground floor bathroom/wet room finished off, It's about 3.6m long by 2.7m wide, tiled from floor to ceiling and has no window in there due to a future extension that will take place on the other side of the rear wall.

Unfortunately, i've Instantly noticed when showering that alot of condensation is forming on the tiles/mirrors and the room stays really wet and humid in there for hours afterwards, which even with the fact we jackoboarded most of the room....its still giving me cause for concern. As I can see wet patches and mould forming on the grout already just a few weeks in.

As part of the bathroom fit, the spark did install a 4" Mentis, Axial type extractor fan in there (pictured). Though doing a bit of research online i'm thinking that this may be the problem as the fan looks quite weak. It has an extraction rate of 73 m3 per hour....and the ducting it's venting through is about 2.5m long...obviously with a right angle bend in it too.... which i've read could well be too long for this fan too?

Anyway long story short, i'm looking at swapping it out for something much more powerful, ideally without having to change the 4" ducting to 6". In-line types not an option as there's no access to the ceiling cavity without making a big hole everytime it hypothetically breaks down.... so i'm guessing from my basic research online that my best bet is to go centrifugal, or mixed type. Either something like the Vent-axia Lo Carbon Quadra/ Vent-axia lo carbon revive, or Airflow Icon60? all seem to have an extraction rate of 220 m3 per hour, so three times as powerful as what i've got now, so hopefully would solve this issue.

Love to get some input on this, am I on the right lines to solving this? are there other things I should be considering too? and has anyone used any of the models above and can comment on their experience? they're all quite expensive so would like to get it right!


pictures below for reference.

extractor_fan_pos.jpgIMG-0909.JPGIMG-0912.JPGIMG-0911.JPG
 
That would give you an air change in roughly 10-12 minutes

Inline ones are always best


i know, it's just that where the inline one would go, would not be accessible with it being a ground floor bathroom. So not sure I can be arsed with the faff of cutting a hole in the ceiling everytime it needs to come down.

I suppose an alternative would be to do a sort of loft hatch instead..... But even then the rate of extraction isn't heaps beyond 220 M3 per hour.

Not sure it's worth it. as a first port of call anyway!
 
i know, it's just that where the inline one would go, would not be accessible with it being a ground floor bathroom. So not sure I can be arsed with the faff of cutting a hole in the ceiling everytime it needs to come down.

I suppose an alternative would be to do a sort of loft hatch instead..... But even then the rate of extraction isn't heaps beyond 220 M3 per hour.

Not sure it's worth it. as a first port of call anyway!

just get the installer back to relocate the fan to above the shower and use the existing ducting!
 
I would move the fan so it’s over the shower 😁
haha, I know, me too... but I dont think it's an option. Let me do another diagram.

Black lines are the joists,
Blue is proposed position of fan over shower and ducting from shower to external
green is soil pipe that cant be moved because of an RSJ.
red is current extractor and current ducting

extractor_over_shower.jpg
 
Last edited:
haha, I know, me too... but I dont think it's an option. Let me do another diagram.

Black lines are the joists,
Blue is proposed position of fan over shower and ducting from shower to external
green is soil pipe that cant be moved because of an RSJ.
red is current extractor and current ducting


How could he get the current ducting from where it is to the shower if the joists run front to back?

I thought you said the red lines were marking where the vent runs ????????
 
i know, it's just that where the inline one would go, would not be accessible with it being a ground floor bathroom. So not sure I can be arsed with the faff of cutting a hole in the ceiling everytime it needs to come down.

I suppose an alternative would be to do a sort of loft hatch instead..... But even then the rate of extraction isn't heaps beyond 220 M3 per hour.

Not sure it's worth it. as a first port of call anyway!

810m3/h

You were reading the lps movement 🙂
 
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Above in my post (20)
Thats beefy indeed. Would mean ripping the ducting out and going bigger but thats not necessarily a bad thing. I reckon it's probably overkill at 800 odd m3 but maybe you're right.

I guess it cant hurt to try a centrifugal one first thats three times the extraction of my current.... and if that doesnt cut the mustard as it were, then I can just go nuclear with an 8'' inline.
 
flexi vent slows the airflow down. Longer runs are far better using soil pipes
Is 2.5m considered long? Ideally I want to try and fix this with the least amount of ceiling coming down as possible.

are some types of flexi better than others? all the inline ones i've got in the loft dont use the aluminium stuff, but they're like a white material instead.
 
Can you push a length of 4” soil pipe in from outside, where your current grill is?
Then connect up a centrifugal fan to that, this would not entail pulling any ceiling down and may be enough to solve the problem.
 
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Can you push a length of 4” soil pipe in from outside, where your current grill is?
Then connect up a centrifugal fan to that, this would not entail pulling any ceiling down and may be enough to solve the problem.

That is my hope yes. It's an odd layout though this house, it was a bungalow at one point and when extra floors were added they retained the original bungalow ceiling, meaning all the cavities between the ground and first floor.... are not run of the mill haha. I recall it being multi cavitied and all sorts of weird stuff in there.

So I think im gonna try the centrifugal first as phase 1. If not good enough, try change the ducting to solid. If still too wet, then keep the solid ducting and go for an inline one.

Maybe a silly question - but can you run a fan with wider ducting than recommended? I can see how running smaller would cause too much back-pressure. But if I bought a 4'' centrifugal, then one of those 4'' to 6'' converter pieces for the ducting, then ran 6'' ducting..... that would be fine?

Asking because I guess then if I DO swap to an inline in future, a 6'' one would be heaps more powerful.... so seems a better strategy overall.
 

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