Abstract: A liner for the reservoir of an evaporative cooler consisting of a tub or trough like article. The liner is made of a thin, flexible, water impermeable material and shaped to fit inside the reservoirs of existing coolers. In addition, the liner has flaps extending upwardly from each side which would fold to fit in between the pads and edges of the reservoir. The flaps provide a means for sealing the reservoir when the pads are in place.