Pentair Skimmer Trimmer Valve Plate Residential fits Admiral S-20 Skimmers. When using the Trimmer Valve Plate Residential, water is drawn by the suction of the pump from the surface of the pool and the main drain line. The flow is balanced by the diverter plate located under the Trimmer Valve Plate Residential. If obstruction or evaporation occurs, causing a significant reduction of flow over the weir, the float will automatically snap shut. This diverts all flow to the pump from the main drain line ad prevents possible air lock. When the pump is shut off or water level condition has been remedied, the float will rise back to the top of the assembly, allowing for normal operation of the flow. In Floor Parts stocks a complete line of Skimmer Trimmer Valve Plate Residential for your Pentair Admiral Skimmer replacement parts.