Abstract: A downhole pump for use in a well which includes a casing, a coaxially aligned tubing within the casing for transporting fluid, and fluid filling the space between the tubing and casing. A bottom seals the casing and tubing and includes an upward-flow check valve which permits fluid flow only from beneath the bottom into the tubing. A bucket having an open top, a closed bottom and an annular fin extending from the side thereof is constrained within the tubing. The bucket bottom also includes an upward-flow check valve. A plunger mounted on the tubing over the bucket cooperates with the bucket to form a cavity, the size of which increases as the bucket moves downward within the tubing. A third upward-flow check valve is mounted on the plunger to permit fluid flow from within the bucket to the tubing over the plunger. Holes are formed in the casing between the bottom and the annular fin of the bucket to permit fluid communication between the casing and lower portion of the tubing.