Condensation in Extractor Pipe from Bathroom

[bobbinboy]

I have an issue with an in line extractor fan setup that runs from my bathroom ceiling through the loft to an outside vent on the soffit. The hose is a 100mm flexible one that runs about 2 metres from the bathroom ceiling to the fan and then about another 6 meters to the outside vent.

I only noticed a problem when the fan which is screwed to a joist stopped working and on investigation I found that the flexi hose had dipped into the gap between the joists either side of the fan and had filled up with water to such an extent that the water had flooded the fan and has probably shorted the fan out. In addition the problem is repeated along the entire length of hose as it runs across the joists and dips down resulting in water build up.

I think there are two issues:

• The flexi hose isn't level and unless supported along its entire length there will always be a build up in the dips - I could support it all the way along using some chipboard flooring but could I solve this with a proper 100mm plastic pipe? As long as it is level or even sloped towards the outside vent would this be an ok?

• On inspection the fan installed was the cheapest 100mm you can get and reading up on the net I have see that this only works up to 3m of hose and the fan simply isn't powerful enough to extract the moist air along the entire length of hose -

If I upgraded the fan to any one of the decent ones available online or in screwfix etc would this be powerful enough to push the moist air to the outside vent? If I upgraded the fan would this enable me to keep the flexi hose (I would support it to ensure no dips).

Also the 2m run of hose from the bathroom to the fan runs slightly up hill as it has to go over a joist. There is nothing I can do about this as it isn't accessible so would a more powerful fan stop the build up of water in this section?

Any advice appreciated?

p.s. when I first found the problem I tipped the pipe up to see the issue and the cold manky water ran back down the pipe to the bathroom vent and poured through onto my daughter having a bath. She was not impressed.....

 

[WabbitPoo]

yep 6m is way too long for a basic fan. i lagged the pipe in my loft, and made sure the fan runs for some time after the shower has done, to help push all steam out. seems to have sorted it. if you can make the hose do all of its "up" in one go, then downhill to the outside world, you'll have problems.

 

[Nige F]

yep 6m is way too long for a basic fan. i.

But then there is another 2 metres - and apparently over the bathroom is inaccesible - I would get access through the bathroom ceiling and put a vent up and out through the roof tiles - and incorporate a condensate drain tee - But then I only have to pay for parts - no idea what the labour cost would be

 

[bobbinboy]

Putting another type of fan in is not an option unfortunately as there is a loft conversion above the current bathroom which is why the current hose will have to do the job.

Wabbitpoo - are you saying I'll still have problems even if the only up hill section is the 1st 2 metres to the fan? Surely making the last 6 metres downhill will help?

Can anyone recommend a powerful silent in line fan?

 

[Wangerman]

If you can re-pipe part of it in 4" and use a condense trap. this allows the water to flow down the pipe and into a 3/4" overflow pipe which connects to it and not back into the fan

You can then discharge the overflow pipe out of the eaves or the wall

I think Mcalpine list this as part no CONTRAP 1

Secondly an in-line fan is generaly more powerful and might pull the distance you require


hope this hepls

 

[Wangerman]

For makes you can't go wrong with XPELAIR or VENT AXIA

 

[JohnD]

try to use a smooth rigid duct such as soil pipe, mostly laid with a fall to the outside vent

and wrap the whole duct in loft insulation to keeo it warm and prevent condensation. Space blanket is very clean to handle for this kind of job.

 

[WabbitPoo]

Putting another type of fan in is not an option unfortunately as there is a loft conversion above the current bathroom which is why the current hose will have to do the job.

Wabbitpoo - are you saying I'll still have problems even if the only up hill section is the 1st 2 metres to the fan? Surely making the last 6 metres downhill will help?

Can anyone recommend a powerful silent in line fan?

I THINK that's what I said...

 

[MJN]

Can anyone recommend a powerful silent in line fan?

Yes, the Manrose SCF200T centrifugal timer fan for only £30-£40.

We've got one serving an en suite which, obviously, is adjacent to a bedroom hence low noise level was a critical requirement, particularly for my other half who can seemingly get woken up by one of our cats 'breathing heavily' (yes, really). You can barely tell its running yet the extraction performance is excellent. I fabricated an anti-vibration mount to isolate it from the rafters however in hindsight it was probably not necessary given how quietly (and smoothly) it turned out to run.

For long ducting runs (>3m) you have little option but to go for a centrifugal fan as an axial fan simply cannot overcome the back pressure. You may find a centrifugal fan will solve your problem in one go given the greater evaporation of the condensate from the higher flow rate, particularly if you utilise the overrun timer (which given the low noise should be entirely acceptable).

You can get insulated ducting hose which might help. As the others have mentioned you can also fit a condensate trap but I'd try and remove the cause before treating the symptom.

Mathew