55 gallon drum, drill a hole in the bottom and seal with an ebb & flow fitting. Connect that fitting to a tube that reaches your reservoir. Drill a hole in reservoir (near the required water level height) for the float valve and connect the tube to it. When the float valve is raised due to water level increasing, it shuts the float valve. When the water level drops, the float falls and opens the valve up. This allows the water from the 55gal drum to fill the reservoir until the float valve raises up again and shuts off the valve. Good luck!