Drainage removes excess water from a site or structure. Water is the most destructive force in construction. It erodes soil, undermines foundations, floods basements, and rots materials. A good drainage system moves water away from the building and off the site. It includes gutters, downpipes, French drains, swales, catch basins, storm sewers, and retention ponds. It is a system, not a single component. In the kitchen, drainage is the sink, the drainpipe, the garbage disposal, and the vent. It removes wastewater from the kitchen. It prevents flooding. It prevents odors. It is the kitchen's drainage system.

Surface drainage handles water on the surface. The site is graded so that water flows away from the building. Swales are shallow channels that direct water to a catch basin or a storm drain. Subsurface drainage handles water below the surface. French drains are gravel-filled trenches with perforated pipes that collect groundwater and carry it away. Foundation drains collect water around the base of a foundation. In the kitchen, the sink drain is a subsurface drain. It carries water from the sink to the sewer. The vent pipe allows air into the system. The trap holds water to seal out gases. The system is simple. The system is essential.

Drainage must be designed. The soil type, the water table, the rainfall, and the site topography all matter. A site that does not drain properly can flood, erode, and settle. In the kitchen, the drain must be sized correctly. It must be vented correctly. It must be trapped correctly. It must be maintained. Grease and food must not be poured down the drain. They will clog it. The drainage is the system. The system is the protection. The protection is the drainage. The kitchen is the building. The cook is the builder. The drain is the drainage. The drainage is the drain. The water flows. The water goes. The kitchen is dry. The cook is happy. The meal is good.