The sketch shows the essential details of a typical B/W submersible pump control installation. Note that the low level cutoff electrode is suspended in the well just above the pump. When the water level is pumped below this electrode, interruption of control circuit automatically stops the pump. Also, on most installations, the pressure switch is wired in series with the load contacts on the relay. Whenever water in the well raise to the upper reset electrode, the pump is automatically re-started - providing the pressure switch still demands a flow of water into the storage tank. Because the electrode suspension wires can usually be brought up from the well in the same conduit as the motor cable or through one of the holes in the sanitary well seal, electrode holders are not normally required for submersible pump installations. NOTE: A ground is required from the indicated relay terminal to the liquid in order to complete the secondary circuit of the relay. In wells an extra common electrode is used, extending slightly below the longest operating electrode used.