US Patent 7426784 Compact fire sprinkler attachment insert

The invention satisfies this need. The invention is an internally threaded insert for use with a polymetric pipe fitting in a fire sprinkler system. The insert comprises an outer side surface, an outer rearward surface and an outer forward surface. The outer forward surface is adapted to retain a fire sprinkler at a forward end of the insert. The outer side surface of the insert is sized and dimensioned so as to closely match the bores of standard polymeric pipe fittings, so as to be capable of being slidably and snugly received into the bores of a standard polymeric pipe fitting. The insert can be conveniently affixed within the bores by non-mechanical means, such as by gluing.