A pipe is a tubular piece or empty cylinder, usually but not necessarily of circular cross-section that is used to transmit substances which can flow, for example - liquids and gases (fluids), slurries, powders and also masses of small solids. Pipes can also be used for structural applications and empty pipe is much harder per unit in weight than solid members. Pipes are used for: • Plumbing • Tap water • Pipelines transporting gas or liquid over long distances • Compressed air systems • Petroleum industry • Pipe bombs Here is the List of top pipe companies: