Abstract: The system prevents water flowing freely up and down an open borehole. A hose of stretch elastic rubber is inserted into the borehole and, once installed, is filled with water from the surface. The hose inflates and expands, plugging the borehole. Used with multi-level sampling apparatus, lengths of the hose plug the borehole between the sampling ports. The lengths of hose are mechanically supported between couplings by means of stiff plastic hose passing inside the hose, between the couplings.

Abstract: A probe is disclosed, for lowering into a water-well or other hole. The probe includes conductivity measuring electrodes, to distinguish between e.g., water and contaminants, such as gasoline. The probe also includes an optical sensing facility to locate the junction between air and liquid. The probe comprises a transparent plastic tube, mounted inside a housing. A beam of light from a LED passes obliquely through the plastic tube and onto a photo-transistor. When liquid is encountered in the well, the liquid enters the tube: the change in refractive index now directs the beam away from the photo-transistor. The optical and conductivity sensors are both actuated at the same depth.