the surface once at the surface the bubbler tube 20 is connected to a stroke pump level switch means 98 which is used to determine the hydrostatic pressure of the bubbler tube and convert the pressure into an electrical signal once the pressure exceeds a predetermined threshold the corresponding pressure data will then be transmitted to the programmable logic controller 100 which in the preferred embodiment is a siemens ti model 545 programmable logic controller generally the predetermined threshold pressure will correspond to the level of fluid in the wellbore which the operator wishes for the pumping unit to pump fluid the programmable logic controller 100 also known as the programmable processing means is used for converting the signal received from the stroke pump level switch to digital computer readable signal storing the data and then comparing the data of the recovery well with other pre programmed functions once the threshold pressure has been surpassed and the signal sent to the processor 100 the processing means generates an output signal which will be received by the solenoid valve 88 the bubbler tube 96 can also have attached thereto a high level switch 102 which is also used to determine the level of the fluid in the wellbore however the switch 102 will activate only once a predetermined high level in the wellbore has been reached this level is generally set a few feet above the.