"Dennis" wrote in message
news:ZbNgf.2937$F%3.2805@trnddc05...
Gary, I just can't agree. There should be no water or snow infiltration in
a properly designed termination. (It has a damper in the exterior cap to
prevent just that.)

By adding unnecessary twists and turns, you are adding some back pressure
for the blower to overcome, which would degrade its performance (to
whatever extent would depend on the specific system.) Also adding a trap
could possibly cause some moisture in the air stream to condense prior to
being evacuated (this would especially true if your roof cap has no damper
and allows rail to enter). This would be undesirable as standing water
could deteriorate the vinyl ducting over time. (I prefer metal ducting as
the high heat in an attic can cause plastics to deteriorate over time).

In any case, a duct that runs as straight as possible is the most
desirable way to vent, and millions of homes exist with roof terminations
where this presents no problems at all.

"gary" wrote in message
news:j6bff.524440$1i.262605@pd7tw2no...
That is done on all new buildings here. I just took a picture of one
today. Can I upload binaries here? Do you really think a slight U in a
4" pipe is going to fill up with water from the minimal amount of snow or
rain that might get into the pipe? If you get that much water in there
the trap is NOT your problem. You have other problems. If you do not
put the "trap" there where do you think that water goes. Right into your
fan, your motor and your grill (if metal) and causes rust.


"Dennis" wrote in message
newsP9ff.22603$5R4.2331@trnddc06...
Your kidding right? Trap the duct?

"gary" wrote in message
newslRef.522479$tl2.34263@pd7tw3no...
Use insulate flex ducting to prevent moisture condensation and put a U
in it so that any water that might get in the pipe through the top of
the vent does not drain back into your fan.








The OP isnt showing, so....

The proper way to run a bathroom vent is simple, and to do it by code is
simpler yet..

If the run is over 14 Feet, it needs to be metal snap lock pipe. Period.
If water is getting into a vent pipe that feeds to the roof, the wrong cover
is on it.
If condensation is an issue, then you have the pipe obviously not ran in the
best location and it should be relocated if possible, and again, if over 14
feet, metal ducting used, and if needed, insulate with proper duct wrap.
Condensation, can also occur when you are using a fan with too low of a CFM
for the space, or, trying, as others have said to make it harder than it
needs to be, and installing a bunch of so called traps (that are not to code
here anyway) and raising the static pressure of a tiny POS fan..unless you
are using Panasonics.