Drains

Drains are channels, pipes, or other conduits designed to remove water or wastewater from an area to prevent accumulation, erosion, or structural damage. They collect liquid from surfaces, equipment, or fixtures and convey it to a disposal point such as a sewer, septic system, or natural outlet. In buildings, drainage systems separate wastewater from clean water and protect against sewer gas infiltration through traps and vents. In civil practice, drainage management targets surface and subsurface water to safeguard infrastructure and land stability.

Common drain types include surface or channel drains equipped with gratings to collect rainwater from pavements and yards; interior sanitary drains that carry waste from sinks, showers, and toilets; roof drains that drain rainwater from roofs; and outdoor storm drains, trench drains, and French drains designed to redirect groundwater or runoff away from foundations and roads. Traps prevent sewer gases from entering spaces, while cleanouts provide access for clearing blockages.

Drainage systems use a range of materials such as PVC, ABS, cast iron, steel, or concrete pipes, with fittings, traps, vents, and backflow preventers. Perforated pipes with surrounding aggregate are used for subdrainage and drainage fields. Proper slope along the horizontal alignment and appropriate fall ensure gravity-driven flow; in some cases pumps or lifts are used when gravity alone is insufficient.

Maintenance includes removing debris, inspecting for leaks, corrosion, and root intrusion, and avoiding chemical drain cleaners that can damage pipes. Regular snaking or hydro-jetting may be required to clear blockages. Codes specify sizing, venting, trap sealing, and backflow protection to prevent wastewater contamination and sewer gases.

Effective drainage improves indoor comfort and health, protects structures, and supports urban flood management by directing water to suitable outlets.