*listing is for one complete dryer ell.  The listing picture shows part A and part B that snaps together to create one 90 degree ell. 

Dryer-Ell 10" Radius Elbows

Every Dryer-Ell increases airflow efficiency and can be measured the same as straight pipe.


Schematic of Dryer-Ell LT90 Development

Model LT90 delivers improved airflow efficiency for ninety degree turns. It is a straight pipe equivalent for most building code including 2009 and 2012 IMC and IRC.

Overcome Length of Run IssuesLT90 PDF Tech SpecificationsLT90 Technical Specifications
LT90 PDF Installation InstructionsLT90 Installation Instruction

The Dryer-Ell has a four-inch diameter (the standard for dryer duct pipe) and an eighteen-inch overall length. Because it is code approved to eliminate run-length penalties, the LT90 is very useful for taking advantage of the maximum allowable exhaust duct length. Its longer radius and smooth interior improve dryer performance and are 500% more airflow efficient than sectioned elbows.

ASHRAE Calculations


Based on the fundamentals handbook methodology for calculating friction loss, the LT90 has an equivalent length of 1.5 feet (or its actual length). You may find full formula details and independent engineering confirmation in the White Papers / ASHRAE Calculations sections. These calculations are recognized in 2006 IRC under section M1502.6 (2009 and 2012 IRC and IMC list the actual length as discussed below).