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Fiberglass Fittings & Joints


FRP duct joint process for underslab installationInstallation & Joining

Generally, for underslab installation, the duct will be installed in a graded trench with good drainage and on a 4” bed of pea gravel, with sand or pea gravel used as a backfill.  The duct will be joined by an internal galvanized sheet metal sleeve held in place by sheet metal screws and then sealed with a UL listed duct sealer.  A wrap of Monoxivent 6” wide polyethylene-backed pressure sensitive tape is placed over the joint and the screw heads.

In order to avoid water infiltration, UnderDuct is manufactured with a resin rich veil on the OD. Watertights joints are made using the wet lay-up method.

Manufacturer’s installation instructions are to be followed.  See separate sheets for wet lay-up method instructions.  The system is to be leak tested prior to backfilling.

FRP Fitting Configurations