A method of forming a structural tube may include urging a substantially flat thermoplastic sandwich sheet against a mandrel and heating the thermoplastic sandwich sheet to a temperature below a glass transition temperature. The method may further include allowing the thermoplastic sandwich sheet to cool and removing the mandrel, thereby forming a tube portion.

A machine for welding saddle connectors by polywelding, during pipe laying, includes a base which extends in a first direction, a clamp which can move along the base in the first direction, a bracket mounting means for detachably coupling the machine to a pipe arranged transversely to the first direction, and a means for detachably coupling the base to the bracket mounting means.

An internal boss can have an outer side surface shaped to match the bored opening of the DWV pipe, an inner side surface shaped to align with an interior pipe surface of the sanitary Tee or Wye fitting component, and an internal face surface of the boss extending between the side surfaces and shaped to align with an interior pipe surface of the DWV pipe when welded thereto. Snap-fit wings can hold the interior face surface of the sanitary Tee or Wye fitting component against an exterior face surface of the DWV pipe while the fitting component and DWV pipe are homogeneously weldable into a single DWV fitting using a solvent mixture including a common plastic material. Related methods and single homogeneous fittings are also provided.

An electrofusion saddle comprising: a thermoplastic body comprising a flange and optionally a spigot which erects from said flange; and a resistance heating coil including multiple windings, wherein said resistance heating coil is partially embedded in said flange and is partially protruding from said flange, wherein the protrusion is of at least 25% of an average external diameter of said multiple windings.