A molded thermoplastic domed end cap, for attachment to the end of an arch shape cross section leaching chamber or stormwater chamber, has a multiplicity of buttresses, to provide facet surfaces where pipe connections may be made. The essentially planar surface portions have tear out or cut out regions, for pipe openings. The buttresses face in different directions, relative to the longitudinal axis of the end cap, to conveniently accommodate pipes running in different angular directions. Pipes, which pass through openings in the surfaces of the buttresses, are supported by molded in step-saddles of the buttresses. Molded in stops limit inward motion of pipes.