(under subclass 105) Devices comprising a pump having a means for causing a portion of the well fluid being pumped to flow back into the well to treat it (e.g., wash it) while the pump is being operated to draw a major portion of the well fluid out of the well.
SEE OR SEARCH CLASS
417, Pumps,
434, for pumps including a separate port or noncyclic valve for draining a pump portion and subclasses 443+ and 446, for pumps with a pressure responsive distributor (e.g., check valve) which may be selectively held open as, for example, to drain the pump.
