Click link for PDF: UnderDuct Installation and Joining Instructions
UnderDuct FRP should be laid in a graded trench with good drainage on a 4” bed of pea gravel. Minimum distance from under the slab to top of duct is 4″ of compacted fill. The recommended maximum is 6′ of compacted fill. Duct can be designed for deeper burial.
Encasement in concrete is not necessary with round UnderDuct. With fiberglass boots in place and sealed, cover with sand or pea gravel and pour floor slab, no delay or tie downs required on round duct.
Duct is manufactured with a resin rich veil on the ID and OD to prevent water infiltration. Where ground water infiltration is possible the field joints should be made using the wet lay-up method as described in the installation instructions.
NOTE: Leak test the system before backfilling.