Pipe

A pipe is a hollow cylindrical conduit used to convey liquids, gases, slurries, or solids through a system of interconnected components. In common usage, pipe refers to a tubular product with standardized dimensions intended for conveyance, while tubes are often selected for structural or mechanical applications where precise outside diameters and wall thicknesses matter.

Pipes are made from a variety of materials, including metals such as steel, cast iron, ductile iron, and copper, as well as plastics such as PVC, CPVC, HDPE, and PEX. Concrete and composite materials are also used in certain applications. Manufacturing methods include seamless production, welding or bending of metal pipes, and extrusion or corrugation for plastics. Joints and fittings are used to connect pipe sections and change direction or diameter.

Sizes and standards vary by region and application. In the United States, nominal pipe size (NPS) and wall thickness classes (such as schedule 40 or schedule 80) are commonly used for metal pipes, while metric systems use DN (diameter nominal) and different pressure ratings. Internationally, standards bodies such as ASTM, ISO, API, and DIN define material specifications, dimensions, tolerances, and testing requirements.

Joints and connections include threaded, welded, brazed or soldered, flanged, and adhesive or solvent-cement methods, depending on material and service. Pipe is often supported by hangers and brackets, protected from corrosion, and insulated or heated where needed.

Common applications span water supply and distribution, drainage and wastewater, gas and oil transport, chemical processing, fire protection, irrigation, and industrial piping networks. Maintenance focuses on leak detection, corrosion control, and ensuring pressure ratings and codes are met.