Guidelines for Proper Duct Venting
All dryer ducting must be a minimum of
4" in diameter. Clean, unobstructed, frictionless
ducts encourage air flow efficiency, quickens drying times,
adds longevity to clothing's life and reduces utility bills.
Flexible transition hose between the dryer
and the wall outlet should be either the foil type or the
aluminum flexible duct (most preferred). Do not use
the plastic or vinyl.
Concealed ducting must be rigid metal (galvanized
or aluminum) duct.
Duct joints shall be installed so that
the male end of the duct points in the direction of the
Joints should be secured with metal tape
(not duct tape). Do not use rivets or screws in the
joints or anywhere else in the duct as these will encourage
Length of concealed rigid metal ducting
shall not exceed 35 feet. Deduct 5 feet from the allowable
length for every 90 degree elbow and two and a half
feet for every 45 degree fitting
is an exception under 2006 IRC Section M1502.6, and included under current IMC Section 504.6.4 and 2009 IRC Section M1502.4).
These lengths may
vary per local codes and dryer manufacturers recommendations.
Dryer venting shall be independent of any
other systems (chimneys or exhaust vents)
Termination of dryer venting must be to
the exterior with a proper hood or roof jack equipped with
a backdraft damper. Small orifice metal screening
should not be part of the hood or roof jack as this will
catch lint and block the opening in a very short time. The
hood opening should point down and exhibit 12 inches of
clearance between the bottom of the hood and the ground
or other obstruction.
Tip to make it easier to attach Aluminum
Flex: Flatten aluminum flex with pipe like dough roller,
to see image.
Actually inspect the termination port of
the dryer and the wall or roof jack. Look for birds
nest or clogged openings. Most importantly, feel for
proper exit velocity of the air leaving the vent and look
at or feel the interior walls of the duct.
If you suspect clogged or partially clogged
exhaust ducting, it is likely you need to have them cleaned.
Dryer vent cleaning improves the safety and efficiency and
depending on the venting circumstances, should be cleaned
or inspected every 6-12 months.
Make sure your flex transition hose is
not kinked or crushed. The space behind your dryer
should be sufficient as to provide adequate room for the
flex transition hose to make its bends with minimal deflection
Dryer vent cleaning is a very real
commercial trade and the contracted work is sometimes described
as Routine and Problem Cleaning.
Look in your Yellow Pages under Duct Cleaning
or search the Internet.
The use of the white vinyl flex pipe is
all but completely prohibited, both by building departments
and appliance manufacturers. Some municipalities allow
or do not discourage the foil covered vinyl flex but almost
all appliance manufacturers insist on the use of the aluminum
flexible pipe. Sister product, the Dryerbox, has a
useful comparison page. Click
here to view it.
Keep exhaust duct as straight and short
as possible. Exhaust systems longer than the manufacturer's
recommendations can extend drying times, affect appliance
operation and may encourage lint build-up on pipe lining.
More Dryer Vent Cleaning information can
be found here.
Great site dealing in all aspects of vent maintenance, cleaning
When running the clothes dryer, be careful not to overdry. Running your dryer too long not only wastes energy but can
also damage your clothes. We recommend using an automatic setting, such as "less dry" rather than a timed setting.
Clean lint filters regularly. Cleaning the lint filters on your washer and
dryer will save energy, improve performance, and minimize fire hazards.
- Routine cleaning is done from the
outside by sending an air-propelled "jet-snake"
through the vent. It blows air 360 degrees backwards,
blasting the lint loose and blowing it outside.
The lint is caught in a special bag.
- Problem Cleaning is performed when
an individual dryer is not drying clothes fast enough.
They disconnect and pull the dryer out, install a large
blower on the vent, and blow, brush, vacuum and/or dismantle
- whatever it takes to get the vent clean.
Ten Inch Radius Smooth Dryer Duct Elbows