Residential Building Knowledge Base
What is the equivalent length of the Dryer-Ell to straight pipe?
For the LT45, the long turn 45 degree elbow (10 inch radius), its is .75 feet or 9"
For the LT90, the long turn 90 degree elbow (10 inch radius), it is 1.5 feet or 18"
Can I use the full length allowed by the dryer manufacturer's specs?
Only if the manufacturer specifically defines equivalent lengths for 10" radius elbows as 18" and 9" for the LT90 and LT45 respectively. Otherwise, you can not mix and match using the code table to eliminate reductions in conjunction with the maximum allowable length defined by the dryer manufacturer.
Why do you suggest that the side seams be taped off?
The Dryer-Ell is designed to save space (and money) for shipping with its two-piece construction. While the fit is very snug thanks to its locking tabs, there still is the possibility of some air leakage without taping the entire length of the seams as well as the circumference of where it connects to the pipe. As well as the loss of airflow efficiency, this can allow moisture to escape which can create a mildew problem down the road. Additionally, UL's confirmation of airflow efficiency was completed with all seams completely taped off.
Why does the building code restrict the allowable run length of a dryer duct?
As Underwriter's Laboratories confirmed when studying the Dryer-Ell, even straight pipe contributes to airflow friction loss. As duct runs get longer (or as sectioned elbows are added) back pressure increases. This makes it more difficult for the dryer to evacuate lint that is normally pumped out from every cycle. If the run is too long, the risk that lint will build up enough to create a fire hazard increases dramatically. This is a very serious threat: According to the US Fire Adminstration, there are more than 15,000 dryer fires every year. The code restrictions are designed to reduce that risk.
I don't see my question listed here. Who can I contact for assitance?
Feel free to drop us an e-mail HERE or give us a call at 888-443-7937. We have engineers and resources we'd be happy to share. Additionally, there is a new (and growing) resource you may find at www.dryerventingforum.com.
Ten Inch Radius Smooth Dryer Duct Elbows