There are described methods and systems for supplying water to an aircraft. A water supply assembly is fluidly coupled to a water storage tank via a supply line. An overflow line is fluidly coupled to the water supply assembly. One or more sensors are configured to determine an amount of water in the water storage tank. One or more processors are communicative with the one or more sensors and configured to: determine a desired amount of water to be contained in the water storage tank; determine from the one or more sensors that an amount of water in the water storage tank corresponds to the desired amount of water; and, in response to determining that the amount of water in the water storage tank corresponds to the desired amount of water, transmit an instruction for causing water being supplied from the water supply assembly to the water storage tank to be diverted to the overflow line.