piston de refoulement

CONT: Un mouvement rapide ascendant et descendant d'un piston de refoulement (purgeur) dans l'eau du puits, renversera alternativement la direction de l'écoulement au travers de la crépine [...]

CONT: Surge-blocks, swabs, or plungers are disc shaped devices made to fit tightly within the well. Their edges are usually fitted with rubber or leather rings to make a tight seal against the well casing. Pipe sections are then attached to the surge-block to lower it into the well, above the well screen, and about 15 feet below the water level. The assembly is then repeatedly lifted up and down. The up and down action of the surge-block creates suction and compression strokes that force water in and out of the well through the screened interval, gravel pack, and aquifer. It works like a plunger in the way that it removes small obstructions and sediments from the well. The surge-block is slowly lowered each time resistance begins to decrease.
CONT: A rapid up and down motion of a surge block in the water of the well will give reversals of flow through the screen ...