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


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