A leak is a way (usually an opening) for fluid to escape a container or fluid-containing system, such as a tank or a ship's hull, through which the contents of the container can escape or outside matter can enter the container. Leaks are usually unintended and therefore undesired. The word leak usually refers to a gradual loss; a sudden loss is usually called a spill. The matter leaking in or out can be gas, liquid, a highly viscous paste, or even a fluidized solid such as a powdered or granular solid or other solid particles.
Types
Types of leak openings include a puncture, gash, rust or other corrosion hole, very tiny "pinhole leak" (possibly in imperfect welds), crack or microcrack, or inadequate sealing between components or parts joined. When there is a puncture, the size and shape of the leak can often be seen, but in many other cases, the size and shape of the leak opening may not be so obvious. In many cases, the location of a leak can be determined by seeing material drip out at a certain place, although the leak opening itself is not obvious. In some cases, it may be known or suspected there is a leak, but even the location of the leak is not known. Since leak openings are often irregular shapes or extended cracks, leaks are sometimes sized by the leakage rate, as in volume of fluid leaked per time, rather than the size of the opening. Common types of leaks for many people include leaks in vehicle tires, which allows air to leak out and results in flat tires, and leaks in containers, which spills the contents. Leaks can occur or develop in many different kinds of household, building, vehicle, marine, aircraft, or industrial fluid systems, whether the fluid is a gas or liquid. Leaks in vehicle hydraulic systems such as brake or power steering lines could cause loss of brake or power steering fluid, resulting in failure of the brakes, power steering, or other hydraulic system. Also possible are leaks of engine coolant—particularly in the radiator and at the water pump seal, transmission fluid, motor oil, and refrigerant in the air conditioning system. Some of these vehicle fluids have different colors to help identify the type of leaking fluid. Batteries are at risk of leakage, because their operation inherently involves chemical corrosion. A zinc-carbon battery is an example of a commonly-seen leaking component; the electrolytes inside the cell sometimes leak out of the cell casing and cause damage to an electronic appliance. Water leaks occur when there is damage to the water supply system or wastewater system that causes water to release. For water suppliers, leakage is defined as the amount of water that enters the supply system but is not ultimately provided to customers. Gas leaks, e.g. in natural gas lines allow flammable and potentially explosive gas to leak out, resulting in a hazardous situation. Leaks of refrigerant may occur in refrigerators or air conditioning systems. Some industrial plants, especially chemical and power plants, have numerous fluid systems containing many types of liquid or gaseous chemicals, sometimes at high temperature and/or pressure. An example of a possible industrial location of a leak between two fluid systems is a leak between the shell and tube sides in a heat exchanger, potentially contaminating either or both fluid systems with the other fluid. A system holding a full or partial vacuum may have a leak causing inleakage of air from the outside. Leakage of even small jets of superheated steam can be extremely dangerous because of the high temperatures and large amounts of energy released within confined spaces. Hazmat procedures and/or teams may become involved when leakage or spillage of hazardous materials occurs. Leaks while transporting hazardous materials could result in danger; for example, when accidents occur. Leakage of air or other gas out of hot air balloons or dirigibles, can be dangerous. Leakage from pressurized cabins of airplanes or spacecraft can cause breathing difficulties to the occupants. Low-pressure chronic leaks of air, rainwater, or melting snow are a common problem in architecture, affecting residential, commercial, and industrial structures. Very small openings in roof or wall cladding can admit large amounts of water over time, especially if wind-driven by storms. Because water can travel long distances horizontally due to surface tension and capillary action, it can migrate to places far removed from the original ingress location. Electronic Leak Detection (ELD) may be required to find elusive pinhole or hidden seam leaks. Because leaks can cause water damage and extensive growth of mold, major lawsuits among building tenants, owners, builders, architects, consultants, and suppliers can ensue. During the design phase, considerable effort is often devoted to prevention of air and water leaks through building envelopes, sometimes including full-scale mockups subjected to testing in specialized wind tunnels. A leak can occur inside a living body, such as a hole in the septum between heart ventricles. Major leaks of blood, known as aneurisms, can cause sudden unexpected death, if not immediately treated.
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