A compression joint seals by deforming a soft metal ring (the olive) between a tapered fitting seat and the pipe wall as the nut is tightened, so the joint depends on the pipe wall resisting the inward crushing force. Because plastic push-fit (polybutylene/PE-X) barrier pipe is compliant rather than rigid, a rigid tubular support insert must be placed inside the pipe bore to restore the hoop stiffness a copper pipe would supply, and a copper (more malleable) olive is specified over a brass one so the sealing ring, not the pipe, takes the plastic deformation. This belongs to domestic plumbing within building services, specifically the sub-topic of dissimilar-material pipe jointing and the compatibility rules governing mixed plastic/copper systems.
A compression joint seals by deforming a soft metal ring (the olive) between a tapered fitting seat and the pipe wall as the nut is tightened, so the joint depends on the pipe wall resisting the inwa…