There are two basic types of subsurface pumps: the tubing pump and the insert pump. The tubing pump barrel is threaded directly onto the bottom of the production tubing, is installed near the bottom of the well, and is immersed in the oil within the well casing. The plunger is run into the tubing on the sucker rod string. Generally, a standing valve puller is run between the bottom of the plunger and the separate standing valve. This makes the removal of the standing valve optional when pulling the sucker rods and plunger. The plunger, traveling valve, and standing valve can be serviced simply by pulling the rods, but it requires removal of the tubing to service the pump barrel.
An insert pump is run into the well on the rods as a complete unit. A seating assembly on the pump engages a seating nipple on the tubing when the pump is run in or installed. After the well has pumped up, the additional pressure of oil in the tubing combined with the flowline pressure holds the pump firmly in place. The entire rod pump is removable and therefore may be serviced by pulling the sucker rod string.