from portions of fig1 for sake of clarity the sucker rod string is connected to operate an oil pump sometimes referred to as the upper pump the pump being identified with the numeral 32 there is a lower pump which will sometimes be described as the water pump the water pump is connected in a common housing with the upper or oil pump the two are anchored on the common packer 26 and the packer 26 serves the purpose of dividing upper and lower chambers for different purposes to be described in addition the packer serves as a landing nipple to fasten or anchor the oil pump 32 the pump 32 incorporates a pump cylinder 34 which encloses a piston 36 the piston 36 is stroked by the sucker rod string 20 the piston 36 raises the column of oil produced oil along with water accumulates to the height 30 shown in fig1 oil is delivered through an opening into the pump 32 not shown and fills the cylinder 34 oil is first collected in the lower portions below the piston 36 on the down stroke of the piston 36 a checkvalve 38 is opened the valve 38 delivers oil in the cylinder 34 above the piston 36 this is the upper chamber the checkvalve 38 operates on the downstroke to enable filling above the piston the piston 36 on the upstroke forces oil out of the cylinder 34 up into the tubing 16 through the standing valve 40 the valves 38 and 40 are checkvalves they are biased so oil is forced into the tubing string 16 this.