This manual is the third edition of AWWA Manual M45, Fiberglass Pipe Design. It provides the reader with both technical and general information to aid in the design, specification, procurement, installation, and understanding of fiberglass pipe and fittings. It is intended for use by utilities and municipalities of all sizes, whether as a reference book or textbook for those not fully familiar with fiberglass pipe and fitting products. The manual covers fiberglass pipe and fitting products and certain appurtenances and their application to practical installations, whether of a standard or special nature. This third edition includes updates to soil classifications that unify the terminology for all piping materials, corrections to the pressure surge calculations, and editorial changes to improve understanding and clarity of content.