Abstract: A constant level of fluid (8 or 106) in vessel (1 or 104) is maintained using a reservoir (5 or 102) and a tank (4 or 101). Float valves (9 or 107) which raise and lower with the level of fluid in the reservoir are used to selectively close off fluid passages (13 or 109) from the tank into the reservoir. Until the desired level of fluid is reached in the reservoir, the reservoir continuously provides fluid to the vessel. Once fluid flow into the reservoir is stopped, flow from the reservoir into the vessel also stops. The vessel can be positioned adjacent to or remote from the reservoir.