Abstract: A valve for controlling the level of solution in a plant container of a hydroponic irrigation system is disclosed. The valve includes a chamber having a top wall with an opening for the passage of liquid therethrough and having an inlet port below the top wall. Hydroponic irrigation solution is pumped into the container by way of the inlet port. A closure member within the chamber is moveable into a position blocking the flow of liquid through the opening by a lost-motion connection to a float and is held in its blocking position, so long as the pump continues to operate, by the pressure of the liquid in the chamber.