Hydrants are valve devices that are used to dispense large volumes of liquid. There are many different types of products. Examples include fire hydrants, flush hydrants, freeze proof hydrants, frost proof hydrants, barrel hydrants, post hydrants, wall hydrants, and yard hydrants. Fire hydrants are the most common type of product. Typically, they are made of metal and then painted red or yellow. Although most fire hydrants are located at ground level, there are several other mounting styles. For example, flush hydrants are installed below ground level, typically in a pit. These active fire protection products are often used near airport runways and other locations that must remain clear of potential obstructions. Wall hydrants are also commonly available. Fire hydrants provide firefighters with convenient access to a municipal water supply. Each hydrant is connected to a large, underground pipe that also carriers water to nearby homes and businesses. Typically, fire hydrants are cylindrical and surrounded by a concrete slab. During a fire call, emergency personnel use a five-sided wrench to open the hydrant’s covers and loosen the stem nut. Fire hoses are connected to the hydrant’s openings and water flows to nearby fire engines. There, pumps are used to increase the water pressure for delivery through a different set of hoses. In cold-weather climates, municipalities may install dry barrel hydrants to avoid the problems posed by freezing temperatures. With a dry barrel hydrant, water does not remain in the upper section after the hydrant valve is turned-off. Instead, an opening allows water to drain from the barrel and onto the nearby ground. The pipe that holds the water is buried beneath the frost line, and the valve that controls the water flow is also located underground. With dry barrel hydrants, a long rod connects the stem nut to the valve. The International Fire Code requires the maintenance of a 36-inch radius around these fire hydrants to prevent obstructions. Post hydrants are thinner than conventional fire hydrants and feature a hose connection, T-handle and casing guard. Frost proof hydrants and freeze proof hydrants locate the valve connection below the frost or freeze line. Typically, wall hydrants are used in commercial and residential applications to provide freeze-protection for an external water supply. Features for all types of hydrants also include compliance with the requirements in American Waterworks Standard C-502. In addition to fire fighting, applications include remote water access, irrigation, gardening, and washing machine hook-ups.