Patent ID: 7121347

Claim:
An apparatus for raising a sample of liquid from a lower level to a higher level, said apparatus comprising a pair of flexible tubes extending alongside each other for extending from the higher level to the lower level, each of said tubes being of uniform bore along its length, a connector linking said tubes at their lower end for defining a generally U-shaped duct, a pig insertable into a first one of said tubes at an upper end thereof and movable along the length of said first tube to a resting position near the bottom of said first tube, said pig being liquid-impermeable and being in contact with the wall of said first tube, means at the upper end of said apparatus for adjusting the pressure in each of said tubes for urging said pig to move either up or down in said first tube in accordance with the applied pressures, and a valve communicating between the inside and outside of said first tube near its lower end but above the resting position of said pig.