Sets out design practice for vertical deflections up to the recommended safe design limit of 5 per cent of the outside diameter for plastics pipes 3 in. and above laid underground. Includes methods for calculating loads, safe bedding depths, and deflections for plastics pipes laid under a number of specified standard laying conditins. For all sizes of pipe below 3 in. diameter, the safe burial depth calculated by This code for the pipe material, degree of compaction of fill, and laying conditions for the 3-in. diameter size may be used.