Percolation is a term used in physics, chemistry, materials science, and geology to describe the movement and filtering of fluids through porous materials. It is the process by which a liquid slowly passes through a filter, such as when making coffee. In geology, percolation refers to the filtration of water through soil and permeable rocks, which flows to recharge the groundwater in the water table and aquifers. Percolation theory is the mathematical study of percolation, which has brought new understanding and techniques to a broad range of topics in physics, materials science, complex networks, epidemiology, and other fields. In places where infiltration basins or septic drain fields are planned to dispose of substantial amounts of water, a percolation test is needed beforehand to determine whether the intended structure is likely to succeed or fail.