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.
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.
The OP isnt showing, so....
The proper way to run a bathroom vent is simple, and to do it by code is
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.
" Through the sidewall or the roof. A poor third would be through the
soffit, which may not be code locally. "
I don't know where venting a bathroom fan out the soffit is a code
violation? Here in NJ most homes are done that way and we are about as
regulated as it gets. I don't see anything wrong with doing a soffit
"What happens is that warm moist air is drawn into the next soffit vent
into the attic space where it can cause damage. Remember that soffit
are normally air inlets. "
I guess that's theoretically possible, but has anyone ever seen it lead
to an actual problem? Bathroom fans are almost always on for a short
time, so any moisture that was introduced should dissipate pretty
quickly. I have a hard time believing that in actual practice, this
is really an issue. It's done on most of the homes here in NJ that
I've seen and hasn't been harmful.
I've got the fan vented thru the soffit. In cold weather the vented air
condenses quickly making it visible. It's quite obvious that it blows away
from the house and does not get sucked back into the adjoining vent.
And thus my house is up to code and yours isn't. there is no difference
between a vented soffit and the attic. I am happy that your insulation
isn't soaking wet, but you won't be working on my house anytime soon.
Hey, the gas furnace usually vents away from the house too, but you
don't put it right next to the window.
Since I merely pointed out that it was not a big deal to put it through
the roof, the same way that the soil stack does for the very same
bathroom, an is not prone to leaks, I think it is your reading
comprehension that is questionable.
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