the well screen 3 into the well casing and is likewise withdrawn as above described an inverted cone or depression d is formed above the interface between the water w and product c as depicted in the drawing this cone of depression d includes a central zone 17 39 comprising the lowest area of the inverted cone d with the product water interface 18 39 being disposed lower than any other part of the product c contained either within the well hole 1 or the surrounding soil s with the foregoing arrangement in mind it will be appreciated that upon operation of the product pump p the contaminating fluid product c will be withdrawn from the body of this fluid contained in the central zone 17 39 check valves v v 39 of any suitable construction are preferably included in each of the withdrawal pipes 8 9 adjacent their respective intakes and will be understood to readily allow upward displacement of fluid through the withdrawal pipes with a minimum of resistance these valves are intended to aid in priming the pumps and facilitate the diffusion of air in the respective fluids being pumped a typical valve would be of the spring loaded plunger type with the above pipe and tube disposition the hydrostatic pressure will be equal both inside and outside the bottom of the separator tube 10 when the pumps are not being operated however due.