ABSTRACT
A piston pump which is a deep well pump has the piston at the bottom of the well. Like centrifugal pumps, positive displacement pumps with a suction lift generally are restricted to about twenty feet of practical lift. There are two basic categories of positive displacement pump: the reciprocating pumps, and the rotary pumps. Under reciprocating pumps are generally included the plunger, or piston pump, the diaphragm pump, and the peristaltic pump. On sludge pumps, the check valves are balls made of hard material; both valve seat and balls will wear and are replaceable. In water utilities, diaphragm pumps are most often used for chemical feed. Peristaltic pumps are not true reciprocating pumps, as they do not have a back and forth action, but they do however, produce a pulsating flow. Chemical slurries, polymers, and sludges are often moved with progressive cavity pumps, a type of rotary pump which can achieve pressures up to 2000 psi, depending on pump length.
