(1)
Underground ducts shall
(a)
be constructed and installed to provide interior drainage from and access to all low points,
(b)
not be connected directly to a sewer, and
(c)
be installed and constructed of materials recommended by ASHRAE and SMACNA Standards and HRAI Manuals.
(2)
A clean-out or pump-out connection shall be provided in an underground duct system at every low point of the duct system.