The Ontario Building Code | Underground Ducts
6.2.3.5. Underground Ducts
(1) Underground ducts shall,
(a) be constructed and installed with a slope to provide interior drainage to all low points,
(b) not be connected directly to a sewer, and
(c) be installed and constructed of materials in conformance with ASHRAE Handbooks, SMACNA Manuals and the HRAI Digest.
(2) A clean-out or pump-out connection shall be provided in an underground duct system at every low point of the duct system.
In Plain Language
Underground ducts must be constructed and installed with a slope providing interior drainage to low points, must not connect directly to a sewer, and must meet other requirements addressing their below-grade exposure.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.