Condensation is forming inside the 100mm pipe above the bathroom vent fan which passes through the cold loft (about 10 feet) to a grill at the apex; the water then drips down through the fan when its off. This is in a flat hence the bathroom has no outside walls and also I can't re-route the 100mm pipe horizontally out of the roof.

This is as was fitted from new (1980's) but the first winter for us hence this must happen every day in cold weather when we take a shower.

Any suggestions to stop the condensation forming?

I've even considered fitting some sort of gravity condensate trap which would have to then have a drain pipe leading out through the eaves.

The vent fan comes on when the lights come on so every visit gets the vent fan being used.

On 12/11/2019 10:34, simon mitchelmore wrote:
Condensation is forming inside the 100mm pipe above the bathroom vent
fan which passes through the cold loft (about 10 feet) to a grill at
the apex; the water then drips down through the fan when its off.
This is in a flat hence the bathroom has no outside walls and also I
can't re-route the 100mm pipe horizontally out of the roof.

This is as was fitted from new (1980's) but the first winter for us
hence this must happen every day in cold weather when we take a
shower.

Any suggestions to stop the condensation forming?

Lag the pipe, to save it losing heat so quickly - that should keep more
of the moisture in suspension for longer.

I've even considered fitting some sort of gravity condensate trap
which would have to then have a drain pipe leading out through the
eaves.

Such things are available:

https://www.toolstation.com/extracto...verflow/p73185


--
Cheers,

John.

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One possible solution is to use insulated ducting:

https://www.i-sells.co.uk/product_in...oducts_id=2465

I believe it is mandatory on new installations under part L. The above company are quite good for having a comprehensive stock of various ducting and their helpline is particularly good at helping you get the right stuff, the bloke I spoke to was very good even though I was only spending approx. £60 with them. Alternatively if your duct is running along the top of the joists just feed your existing insulation over the top of it. I am not sure if it will entirely solve the condensation issue but will surely limit it..

Richard

The example above was just the first one that came up did not notice it was 400mm but the more standard domestic types are available from the same supplier.

Richard

On 12/11/2019 11:45, Tricky Dicky wrote:
One possible solution is to use insulated ducting:

https://www.i-sells.co.uk/product_in...oducts_id=2465

I believe it is mandatory on new installations under part L. The above company are quite good for having a comprehensive stock of various ducting and their helpline is particularly good at helping you get the right stuff, the bloke I spoke to was very good even though I was only spending approx. £60 with them. Alternatively if your duct is running along the top of the joists just feed your existing insulation over the top of it. I am not sure if it will entirely solve the condensation issue but will surely limit it.

Richard

I got this not in extractor fan ducting but in foul stack venting.
The pipe ran horizontal and exited under the eaves high up.

It sagged, watre bollected at a low point and te joint wasnt very
hood...and water ended up dripping down a wall below.

All my vents now slope down towards the outside


--
€œIdeas are inherently conservative. They yield not to the attack of
other ideas but to the massive onslaught of circumstance"

- John K Galbraith

On 12/11/2019 11:45, Tricky Dicky wrote:
One possible solution is to use insulated ducting:

https://www.i-sells.co.uk/product_in...oducts_id=2465

I believe it is mandatory on new installations under part L. The above company are quite good for having a comprehensive stock of various ducting and their helpline is particularly good at helping you get the right stuff, the bloke I spoke to was very good even though I was only spending approx. £60 with them. Alternatively if your duct is running along the top of the joists just feed your existing insulation over the top of it. I am not sure if it will entirely solve the condensation issue but will surely limit it.



NHBC require it when in a loft (as did the 1980's Dr Who props
department to make aliens)

The 4" stuff (as you later pointed out) is a bit cheaper-


--
Adam

Thanks guys, really helpful, obviously its more a common than I thought.

On Tue, 12 Nov 2019 02:34:40 -0800, simon mitchelmore wrote:

Condensation is forming inside the 100mm pipe above the bathroom vent
fan which passes through the cold loft (about 10 feet) to a grill at the
apex; the water then drips down through the fan when its off. This is in
a flat hence the bathroom has no outside walls and also I can't re-route
the 100mm pipe horizontally out of the roof.

This is as was fitted from new (1980's) but the first winter for us
hence this must happen every day in cold weather when we take a shower.

Any suggestions to stop the condensation forming?

I've even considered fitting some sort of gravity condensate trap which
would have to then have a drain pipe leading out through the eaves.

The vent fan comes on when the lights come on so every visit gets the
vent fan being used.

Consider fitting a humidistat?

It may be that you are not clearing out all the humidity if the fan is
linked to the light switch.

In theory after a while the warm air should clear all the humidity out.
Granted that when it cools down there could still be some condensation but
this might reduce it enough to stop the dripping.

Cheers



Dave R


--
AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64

simon mitchelmore wrote

Condensation is forming inside the 100mm pipe above
the bathroom vent fan which passes through the cold
loft (about 10 feet) to a grill at the apex; the water then
drips down through the fan when its off. This is in a flat
hence the bathroom has no outside walls and also I can't
re-route the 100mm pipe horizontally out of the roof.

This is as was fitted from new (1980's) but the first
winter for us hence this must happen every day in
cold weather when we take a shower.

Any suggestions to stop the condensation forming?

Insulating the pipe might reduce the condensation but not eliminate it.

I've even considered fitting some sort of gravity condensate trap which
would have to then have a drain pipe leading out through the eaves.

Yeah, thats the only really viable approach.

The vent fan comes on when the lights come
on so every visit gets the vent fan being used.

It wouldnt be hard to fix that.

On Wed, 13 Nov 2019 08:05:27 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


It wouldn¢t be hard to fix that.

Somebody needs to fix YOU, senile cretin!

--
Website (from 2007) dedicated to the 85-year-old trolling senile
cretin from Oz:
https://www.pcreview.co.uk/threads/r...d-faq.2973853/

This seems to be common in bathrooms with extractors. Indeed another issue
seems to be mould growing in the pipe as well, which can be an issue for
those with allergies.

Brian

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This newsgroup posting comes to you directly from...
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Note this Signature is meaningless.!
"Rod Speed" wrote in message
...
simon mitchelmore wrote

Condensation is forming inside the 100mm pipe above
the bathroom vent fan which passes through the cold
loft (about 10 feet) to a grill at the apex; the water then
drips down through the fan when its off. This is in a flat
hence the bathroom has no outside walls and also I can't
re-route the 100mm pipe horizontally out of the roof.

This is as was fitted from new (1980's) but the first
winter for us hence this must happen every day in
cold weather when we take a shower.

Any suggestions to stop the condensation forming?

Insulating the pipe might reduce the condensation but not eliminate it.

I've even considered fitting some sort of gravity condensate trap which
would have to then have a drain pipe leading out through the eaves.

Yeah, that's the only really viable approach.

The vent fan comes on when the lights come
on so every visit gets the vent fan being used.

It wouldn't be hard to fix that.

On 13/11/2019 07:15, Brian Gaff (Sofa) wrote:
This seems to be common in bathrooms with extractors. Indeed another issue
seems to be mould growing in the pipe as well, which can be an issue for
those with allergies.

Brian



https://www.electricaldirect.co.uk/p...h-spout-363005