Abstract: A captive air system for a water well. A submersible type pump is located downhole in a wellbore for pumping water from an aquifer to the surface of the earth. A special storage tank is buried below the surface of the earth. The tank has a relatively short vertical leg connected to a relatively long lateral leg which slopes downwardly away from the vertical leg. A water supply conduit is located at the lower end of the lateral leg. The pump outlet is connected to the interior of the vertical leg. A blowdown pipe is connected to the bottom of the vertical leg. The edge portions of the tank which join together the vertical and lateral legs serve as a dam so that as the liquid level in the storage tank is lowered, debris always remain in the bottom of the vertical leg while clean fresh water is delivered by the lateral leg.