Without a Bottom Discharge Valve the particulates can settle around the outside of the pump in the stagnant area above the hold-down and stick the pump in the seating nipple, preventing it from being retrieved with the sucker rods. This undesirable condition causes a tubing string to be pulled "wet" since the fluid cannot be drained.

    The Harbison-Fischer Bottom Discharge Valve produces about twenty percent of the fluid through ports just above the standing valve, effectively keeping the fluid between the pump and the tubing in motion and preventing sand from settling above the seating nipple. A secondary benefit is that chemicals used for fighting corrosion are circulated through this normally stagnant area, protecting the outside of the pump from corrosive attack.