Abstract: A geothermal pump includes a lineshaft, an internal casing disposed concentrically around the lineshaft and configured to form a lubrication-space between the lineshaft and the internal casing, an external casing disposed concentrically around the internal casing and configured to form a brine-space between the internal casing and the external casing, a piping network connected to an above-ground end of the internal casing, and a seal assembly disposed on a down-hole end of the lineshaft and connected to the piping network and the lubrication-space, such that a fluid circuit is formed, the seal assembly being configured to enable a lubrication fluid to flow from the piping network to the lubrication-space in a direction toward the above-ground end of the lineshaft while restricting the lubrication fluid from flowing toward the down-hole end of the lineshaft.