Herein is disclosed an in-situ system for automatically washing the walls of a wet well. The system includes a high pressure water pump coupled to a plurality of elongated high pressure water spray heads mounted along the walls of the wet well. The high pressure water spray heads are each coupled to the water pump via a solenoid valve which is in turn coupled to a control panel. The control panel is configured to operate the spray heads one at a time so that the wet well is washed by operating only one spray head at a time. The system uses standard municipal water line as a water source and uses inexpensive motors, pumps and fittings.