The right well pump depends on factors like whether the well is shallow or deep and the diameter of the well casing. Centrifugal pumps are typically the cheapest and best for shallow wells. They work by generating suction through an internal fan. Submersible pumps are the most popular due to the fact that they can typically be installed in both shallow and deep wells. Jet pumps are the most powerful type of well pump, but also more expensive than submersible pumps. Pumps are rated in gallons per minute (GPM). The correct size pump for your well system depends on the number of appliances and fixtures and the number of occupants in the home.