Drainpipes

Drainpipes are pipes that convey liquids away from buildings or structures, forming part of both sanitary drainage and stormwater systems. They include interior sanitary drainpipes that carry wastewater from fixtures to the building sewer or septic system, as well as exterior downpipes that convey roof runoff to storm drainage or ground. Drainpipes are designed to promote gravity flow and are typically vented to prevent trap siphonage and to maintain drainage efficiency.

Materials and construction vary by era, climate, and application. Common materials include PVC or uPVC, ABS plastics, cast iron, copper, clay, and concrete. Sizes depend on function, with interior sanitary drainpipes usually larger than 2 inches in diameter and roof downpipes commonly in the 2 to 4 inch range. Joints may be glued or solvent-welded for plastics, or mechanically joined for metals and clay. Proper slope, appropriate connections, and access for cleaning through cleanouts are essential for reliable operation.

Installation considerations center on flow, venting, and connections to other drainage components. Drains must be sized and sloped to maintain gravity-driven flow, vented to prevent siphoning, and correctly connected to stacks, traps, or sewers as required by code. Roof downpipes should channel water away from foundations, and exterior piping may require protection from freezing. Local building codes and standards govern materials, installation methods, and inspection requirements.

Maintenance and problems commonly involve blockages from hair, grease, sediment, leaves, or roots, and deterioration from age or corrosion. Regular cleaning with mechanical augers or high-pressure jetting is typical; avoid harsh chemical drain cleaners that can damage pipes. Signs of trouble include slow drainage, gurgling, odors, or leaks, which may necessitate inspection, repair, or replacement of sections.

Regulation and terminology vary by region. Drainpipes are typically covered under plumbing codes such as the International Plumbing Code or Uniform Plumbing Code, with regional amendments. The term “downpipe” is often used for roof drainage, while “drainpipe” refers to sanitary waste piping inside a building.