double containment piping apparatus for pressure and non-pressure drainage applications for the transport of hazardous waste, petrochemicals and landfill effluents and for the collection and discharge of large volumes of fluids generated by tank or pressure vessel ruptures and the like consisting of an inner or primary pipe contained within an outer or secondary containment pipe, both fabricated of plastic and/or metal, combined with metal transitional and branch fittings, elbows and flanges, centering units, interstitial supports for inner piping; manually operated metal valves, centrifugal pumps, piston pumps, sump pumps, diaphragm pumps, leak detection apparatus, measuring gauges, automatic valves, plumbing fittings; namely, valves, traps, floor sinks and cleanout fittings for the conveyance of chemicals, plastic transitional and branch fittings; namely, elbows and flanges, plastic centering units, interstitial supports for inner piping and manually operated plastic valves