Abstract: Apparatus for transferring liquid from a first tank to a second tank having supply line coupled to the first tank, a fill line connected to the second tank, a return line leading to the first tank or a sump, a pump for causing liquid to flow from the supply line to the fill line when the apparatus is in a fill mode, from the fill line to the return line when the apparatus is in a purge mode, and a programmable control for placing the apparatus in a purge mode in response to any one of the following signals, a signal indicating that the fill line is not properly attached to the second tank, a signal indicating that the liquid in the second tank has reached a given level, and a signal that the volume of liquid delivered by the pump is that which will fill the second tank to the given level. The programmable control detects leaks and checks whether the rate at which the pump delivers liquid is within a given range.